Commercial diving in Toronto and the Great Lakes: a local guide

By DiverHire

Paid underwater work around Toronto, Lake Ontario and cottage country covers dock and crib inspections, boat-lift and mooring checks, hull and running-gear work, zebra and quagga mussel removal, and recovering things dropped off docks. Lake Ontario's surface only averages 14 °C or warmer from June to October, so the season is short. In Ontario, paid work like this is a "diving operation" under O. Reg. 629/94. That means at least three people on site for a scuba job and, outside emergencies, at least 24 hours' notice to the Ministry. You are paying for that crew, not just the minutes underwater.

What underwater work do Toronto boaters and cottagers hire divers for?

• Dock and crib inspections. Cribs, pilings and rock fill under docks stay out of sight until something shifts; a diver can film them. See underwater inspection.
• Boat lifts and moorings. Checking lift legs and pads, mooring blocks, chain and shackles, or freeing a fouled line.
• Hull and running-gear checks. Props, shafts, outdrive legs, raw-water intakes and anodes. See boat cleaning.
• Mussel removal. Clearing zebra and quagga mussels from running gear, intakes and dock hardware (more below).
• Lost-item recovery. Phones, keys, rings, sunglasses and tools off the end of a dock (see lost ring, phone or keys in a lake). Bigger recoveries sit under salvage operations.
• Marina work. Slip hardware, pilings, intake screens and underwater cleanup.

When is diving season in Toronto and on the Great Lakes?

Summer into early fall. NOAA's Great Lakes Environmental Research Laboratory publishes a daily, satellite-based lake-wide surface temperature for each lake (the GLSEA series). Averaged by month for 1995 to 2025:

Source: NOAA GLERL CoastWatch GLSEA daily lake averages, 1995 to 2025. Monthly means calculated by DiverHire, September 2026.

How to read it:

• Lake Ontario peaks in August at about 22 °C and is still around 9 °C in November. Lake Huron, of which Georgian Bay is part, runs about two to three degrees colder from June to September.
• Years differ a lot. June has averaged anywhere from 10.8 °C to 18.0 °C on Lake Ontario. Plan spring work from the current reading, not the calendar. On 27 September 2026 the Lake Ontario average was 18.7 °C.
• These are surface numbers. From late spring to early fall, lakes in temperate climates can stratify: cooler, denser water settles to the bottom, separated from the warm surface layer by a thermocline where the temperature changes quickly (Michigan Sea Grant). A diver working near the bottom in deeper water can be in colder water than the table shows.
• Muskoka's inland lakes are not in this dataset.

Zebra and quagga mussels: can they damage my boat?

Yes, mostly in the parts you cannot see. Zebra mussels were first found in the Great Lakes in Lake St. Clair in 1986, and quagga mussels near Lake Erie in 1989. They clog water intake lines, and the Invasive Species Centre warns that "small mussels can get into engine cooling systems causing overheating and damage."

An undated Canadian boating site says the mussels do not attach to hulls protected with antifouling paint (Pat's Boating in Canada). On a boat that stays in all season, have the diver check the unpainted parts: props, shafts, outdrive legs, intake grates and through-hulls.

Adult mussels spread between lakes by attaching to boats. If you trailer a boat between lakes, guidance on killing hitchhikers varies by source:

The water temperatures do not agree. In Ontario, follow the Ontario government figure. The province also asks boaters to clean plants and mud off the boat, motor and trailer, and to drain standing water from the transom, live wells and motor intakes.

Freshwater differences: anodes and electric shock drowning

Use magnesium anodes in fresh water

Boating Magazine recommends magnesium anodes for fresh water because they "work better in fresh water's lower-conductivity environment." Zinc, it says, "forms an insulating oxide film over itself, especially in fresh water, that stops it from working." The same article warns that a freshwater boat on magnesium anodes left in a saltwater slip for a week is "a catastrophe". If your boat came from the coast still wearing zincs, ask about switching; see our boat zincs and anodes guide.

Electric shock drowning is mainly a freshwater hazard

Electric shock drowning (ESD) happens when electrical systems at marinas, private docks or on boats leak current into the water. Current passing through a swimmer can cause paralysis that leads to drowning (NFPA). NFPA says fresh water poses a particular risk because the body conducts better than fresh water does, and that ESD is "far more common in freshwater lakes, rivers, and marinas" (NFPA blog, 2026). The Electrical Safety Foundation International says as little as 10 milliamps can cause paralysis and drowning, with no visible warning (ESFi fact sheet).

The Electric Shock Drowning Prevention Association publishes a protocol for diving on boats at docks. Its key steps:

• The boat being worked on is UNPLUGGED, not just switched off at the pedestal, with a lockout tag on the receptacle and breaker.
• Boats next to it are unplugged too.
• The diver checks in with the marina, ideally with a buddy on the dock who knows where to cut power and can call 911.
• At the slightest tingle, the diver stops and leaves the water.

At a cottage, tell the diver what is powered on or near the dock (lift motors, lights, pumps) and switch it off at the breaker before anyone goes in.

What does Ontario law require when you hire a diver?

Paid underwater work in Ontario falls under O. Reg. 629/94, Diving Operations, made under the Occupational Health and Safety Act. A "diving operation" includes underwater inspection, repair or maintenance of structures or ships and the salvage of sunken property. Recreational diving and snorkelling are exempt, and so is a voluntary dive whose sole purpose is to respond to an unforeseen emergency involving imminent danger to someone's life, health or safety. A dive is not voluntary if the diver is paid (s. 2).

Your duties as the owner

"When you hire a diver or diving contractor for a job, including retrieving property ... or to inspect or repair your property, you have many of the same responsibilities of constructors and employers engaged in a diving operation." (Ontario.ca)

In the regulation, that means:

• Notice to the Ministry. The owner, employer and constructor must each ensure the Ministry gets notice at least 24 hours before diving starts. It can be written, or oral followed by writing within five days (s. 5). For emergency recovery, inspection or repair, oral notice must come before diving equipment is moved to the site.
• Notice to others nearby. Law enforcement agencies responsible for the area (the regulation's examples include harbour masters and police), any industrial plant within 2 km that might discharge harmful effluent, and any water control facility or water intake plant within 1 km, at least 24 hours ahead except in an emergency (s. 9).
• Plans. A written operational plan and contingency plan for the dive (s. 7).
• Hazards. Before the dive, any hazardous water flow must be identified and locked out or controlled, and hazardous mechanisms dealt with under clause 4.5.4 of CSA Z275.2-11 (ss. 54 and 55).

What a legal crew looks like

• Scuba needs three people minimum: at least one diver, one standby diver and one tender on site. The supervisor may double as standby diver or tender, but one person cannot be both tender and standby (s. 37).
• Some jobs cannot be done on scuba, including work deeper than 100 feet, near an operating underwater intake, or with power tools or a hoisting device (s. 36). Those jobs need surface-supplied gear.
• Every diver is tethered by a lifeline or strength member, with narrow exceptions (s. 18), and connected to the dive site by two-way communication, voice or line signals (s. 19).
• Competency must meet CSA Z275.4-12 (s. 4.1). The Diver Certification Board of Canada (DCBC) certifies occupational divers to CSA Z275.4. Its certificates include Occupational SCUBA Diver, Restricted Surface Supplied Diver (to 30 m) and Unrestricted Surface Supplied Diver (to 50 m) (DCBC). Ontario says recreational divers who want to work commercially must first go through the DCBC's assessment and training.
• Equipment rules point to specific clauses of CSA Z275.2, such as for cylinders, harnesses and scuba gear; the regulation cites the 2011 edition. The Canadian Association of Diving Contractors says the upcoming CSA Z275.2-26 confirms the "default minimum SCUBA crew" as four people: two divers (one as standby), a tender and a supervisor. A three-person crew may be considered only under restricted conditions, including a controlled environment no deeper than 18 m. The Ontario regulation still sets three, but if a contractor quotes four people for a simple dock job, this may be why.

Diving in Toronto harbour

PortsToronto (the Toronto Port Authority) says diving in the Port and Harbour of Toronto is prohibited unless a Harbour Master Authorization is issued first, under the federal Port Authorities Operations Regulations. Its older Practices and Procedures, dated "as at June 2000" but still linked from its harbour navigation page, say no diving, "commercial or otherwise", may happen without first notifying the Authority and executing the appropriate documents; diving in a navigable channel needs written authorization; and diving operations must display the required signals. Check current requirements with the Harbour Master's Office before any harbour dive.

Permits for dock and shoreline repairs

An inspection dive alters nothing, but repairs can trigger permits:

• Province (Crown land and shore lands). You may need a work permit to place a structure touching more than 15 square metres of shore lands that are Crown land or close to it; floating parts do not count. The beds of most lakes and rivers are Crown land, and a conservation authority or municipal permit does not replace this one. Federal waters, such as parts of the Trent-Severn Waterway, are excluded (Ontario.ca).
• Fisheries and Oceans Canada. DFO has a code of practice for "Boathouses, docks and moorings: Construction, maintenance and repair". You notify DFO that you are using it; if you can follow all its measures and meet all its conditions, DFO does not need to review the project (DFO).
• Toronto region. Alterations to the Lake Ontario shoreline or to watercourses may need a permit from the Toronto and Region Conservation Authority under O. Reg. 41/24 (TRCA).

Why you should not go in after it yourself

In July 2020 a man died after being pulled from Lake Ontario near Ontario Place. Police told Global News that, according to information they received, he "had dropped his phone in the water and went in to retrieve it". Crews were called at 11:57 p.m., and he later died in hospital (Global News). We mention it with respect for him and his family, because the impulse is so understandable. The report does not say what went wrong in the water, but the risks near docks are often ones you cannot see: dark water, cold water below the surface layer, and possible stray current from powered docks and boats.

Mark the spot from the dock, note the rough depth, and call someone equipped and insured to do it. Our lost-item guide has the first-hour steps.

What does a diver cost around Toronto?

We could not verify published rates for Toronto-area or cottage-country dive work, so we do not print one. Here is what drives quotes.

Crew size drives much of the cost. The legal minimum for scuba is three people; the upcoming CSA standard's default is four. Canada's Job Bank publishes wages for the occupation group that includes commercial divers (NOC 72999, which also covers other trades):

Source: Job Bank, Commercial Diver in Ontario wages, 2023 to 2024 data, updated November 2025.

At the Toronto median, three people cost about CAD 90 an hour in wages alone, before equipment, insurance, travel, paperwork and margin. These are employee wages, not a contractor's rate.

Other things that move the price:

• Method. Jobs that rule out scuba (s. 36, above) need surface-supplied equipment.
• Access and travel. A boat-access island in Georgian Bay is a longer day than a Mississauga marina.
• Notice and timing. The 24-hour Ministry notice limits same-day work outside real emergencies.
• Conditions. Depth, visibility, water temperature, weather, and any power shutdown the marina has to arrange.
• What is found. Heavy mussel growth or a failing crib turns a quick look into a longer job.

For comparable quotes, send every diver the same written scope, including what is powered nearby; the planning and pricing guide shows how.

How to hire a diver in Toronto or cottage country

1. Write down the job: location, depth if known, what to inspect, recover or fix, and photos from the surface.
2. Ask to see the DCBC certificate or other proof of competency to CSA Z275.4.
3. Ask who files the Notice of Diving Operation with the Ministry (and get a copy) and, for a site in Toronto harbour, who gets the PortsToronto Harbour Master Authorization.
4. Confirm the crew size and the supervisor. For scuba, expect at least three people.
5. Agree which boats, lifts or dock circuits get unplugged or switched off, and by whom.
6. Check insurance yourself and get it confirmed in writing.
7. If repairs follow, check the permit rules above before work starts.
8. Get the price and the deliverable (video, photos, written report) in writing.

For larger jobs, the Canadian Association of Diving Contractors has a procurement guide; it stresses that "recreational scuba training is not a substitute for occupational diving competency." Our how to hire a diver checklist covers the rest.

For divers: working in Ontario

Divers with commercial competency to CSA Z275.4 can check the Toronto diving jobs page and create a free diver profile.

Hiring a diver through DiverHire

DiverHire is a new marketplace in public beta, started by a Toronto diver (founder's profile), with only a few divers listed so far. You post a job free, divers bid, and you arrange the work and payment directly with the diver you choose; DiverHire charges no fee on jobs and does not employ divers or do the work. It reviews uploaded certificates for a verified badge, but check certification, insurance and the Ministry notice yourself. Local pages: Toronto, Mississauga, Detroit and Montreal.

Sources

• NOAA GLERL CoastWatch: Average Surface Water Temperature (GLSEA): daily lake-wide surface temperatures for Lake Ontario and Lake Huron, 1995 to 2026; monthly means calculated by DiverHire (accessed 2026)
• Michigan Sea Grant: Dissolved Oxygen and Lake Stratification: summer thermal stratification and the thermocline (accessed 2026)
• Ontario e-Laws: O. Reg. 629/94 Diving Operations: scope and exemptions (ss. 1, 2), notice (ss. 5, 9), plans (s. 7), CSA Z275.4-12 competency (s. 4.1), scuba limits (s. 36), minimum scuba crew (s. 37), lifelines and communications (ss. 18, 19), water flow and mechanism hazards (ss. 54, 55) (version in force from 1 July 2025, last amended by O. Reg. 140/25; e-Laws current to 24 September 2026)
• Ontario.ca: Working divers and commercial diving operations: owner duties when hiring a diver, 24-hour notice, DCBC route for recreational divers (updated 2022)
• DCBC: Certificates: certificate types and depth limits; certification to CSA Z275.4 (accessed 2026)
• CADC: Important changes in upcoming CSA Z275.2-26: four-person default scuba crew and three-person conditions (2026)
• CADC: New procurement guide for diving services: hiring guidance for clients (2026)
• PortsToronto: Marine permits and authorizations: diving prohibited unless a Harbour Master Authorization is issued first (updated 2026)
• PortsToronto: Practices and Procedures: notice, written authorization in navigable channels and signals for diving in the Port of Toronto (as at June 2000; check current rules)
• PortsToronto: Harbour navigation: links the Practices and Procedures and says they are enforced by the Toronto Police Marine Unit (accessed 2026)
• Ontario.ca: Crown land work permits: 15 square metre shore-lands threshold, Crown lakebeds, federal waterways (updated 2026)
• DFO: Codes of practice: boathouses, docks and moorings code; notify DFO, no review needed if all measures and conditions are met (modified 2026)
• TRCA: Planning and permits: shoreline and watercourse permits under O. Reg. 41/24 (accessed 2026)
• Invasive Species Centre: Zebra and quagga mussels: first-found dates, spread on boats, clogged intakes, engine cooling damage (accessed 2026)
• Tip of the Mitt Watershed Council: Zebra mussels: 104 °F high-pressure rinse or 5-day dry (modified 2025)
• Pat's Boating in Canada: Zebra mussels: antifouling, up to 5 days out of water, 3+ hot dry days, 140 °F engine flush (undated)
• Ontario.ca: Invasive species in Ontario: clean, drain, dry; five sunny days, over 50 °C or over 250 PSI (updated 2026)
• Boating Magazine: Choosing the right sacrificial anode: magnesium for fresh water, zinc oxide film, magnesium in salt water (2023)
• NFPA: Protect yourself from electric shock drowning: definition of ESD, advice for swimmers and boat owners (accessed 2026)
• NFPA blog: Protecting our loved ones from electric shock drowning: ESD far more common in fresh water (2026)
• ESFi: Electric shock drowning fact sheet: 10 milliamps can cause paralysis (2017)
• ESDPA: Protocol for diving on boats at docks using electrical power: unplugging, lockout, check-in and diver steps (2019)
• Global News: Man dies after drowning in lake near Ontario Place: police account of the July 2020 death after a man went into the lake to retrieve his phone (2020)
• Job Bank: Commercial Diver in Ontario, wages: Toronto Region and Ontario hourly wages, NOC 72999 (2023 to 2024 data, updated 2025)

Last updated: September 2026. Prices and rules change; confirm with local providers.