Underwater and Marine Services: The Full List
A contractor hangs a dewatering blanket over a wooden fender; a municipal superintendent watches a diver sink under the tank riser; a port engineer reviews a cracked weld report from last month's underwater inspection. All three are buyers of commercial diving services, and all three need to know exactly what the work involves before they issue an RFP. This page is the navigational hub for every service we carry. It is a plain-language rundown of the underwater and marine trades: how each job is performed, who is qualified to do it, what the deliverables look like, and how the pricing is built. The 21 services are organized here under logical headings, and each one links to a dedicated lander with details. Regulatory standards are referenced throughout: OSHA 29 CFR 1910 Subpart T for diver safety, ADCI consensus standards for dive supervision, NBIS for bridge inspections, AWWA M42/C652 for potable water tanks, and 46 CFR 71.50-3 for in-water vessel exams. We do not cover recreational scuba here—commercial diving is a different craft with different credentials.
Underwater Inspection and Cathodic Protection
Underwater inspection is the most common reason a municipal owner or bridge engineer calls a dive contractor. A Level II or Level III commercial diver, working from a surface-supplied system, records video, takes probes, and measures concrete and steel. The dive plan is simple but the reporting is not. For bridges, 23 CFR 650.311 sets the inspection interval and the dive team leader must hold FHWA-NHI qualification. For water tanks, AWWA M42 gives the inspection interval and AWWA C652 covers disinfection after the work; any material that contacts potable water must meet NSF/ANSI 61. Underwater inspection is billed by the day, plus equipment and report preparation costs. Cathodic protection inspections look at anode wear and pipe-to-soil potentials; anodes are changed out by divers when readings fall below design. Most contractors require a two-diver team by ADCI standards. The deliverable is a video log, a written report, and a recommendation for follow-up.
Seawall, Bulkhead, and Dock Repair
Seawalls and bulkheads are the heavy steel or concrete members that hold fill. When they fail, the fix is usually underwater concrete placement, new king piles, or tieback replacement. You don't dewater a harbor to do this; divers work in the wet. Seawall repair pricing is by linear foot; it varies with water depth, upland access, and the amount of exposed steel. Bulkhead repair is the same trade. Dock and pier repair covers fenders, deck piles, and bent replacement. A contractor may set a cofferdam around a pile, then divers go down to seal the skirt. Underwater repair crews follow USACE EM 385-1-1 on Corps projects; for other public and private work, OSHA 29 CFR 1910 Subpart T governs the dive team. The critical factors are corrosion and overloading. A complete quote is only possible after a diver-led survey to measure actual damage. Never let a contractor price underwater structural repair on photographs alone.
Pile Driving, Marine Construction, and Boat Lifts
New work is the other side of the trade. Pile driving is done from a spud barge or a dedicated rig. The pile type—steel H, pipe, prestressed concrete—tells you which hammer to use. Vibratory hammers drive sheet and pipe quickly, impact hammers set pipe and H-piles to grade. The diver's job is to inspect the toe, clear obstructions, and handle the jetting or cut-off. Marine construction includes everything from a bulkhead rebuild to a small-craft launching ramp. You supply an engineered plan; the contractor mobilizes the barge, crane, and crew to the site. Boat lift installation is a good example of skilled dive work: divers set the pads, level the frame, and run the hydraulic lines. Pricing for new construction is built from mobilization, day rates for the crew and barge, and material quantity. Pile driving is quoted per pile or per ton driven. If the project is in a harbor, you'll also need to plan around marine traffic and tide windows.
Underwater Hull Cleaning and Propeller Repair
A vessel owner may call to clear a fouled hull or to change a prop without docking. Hull cleaning uses diver-held brushes and water jets to remove slime and calcareous growth. The work is regulated by local water quality agencies; you need a permit to filter debris, and the effect of cleaning on antifouling paint must be considered. Pricing is by foot of waterline or by total underwater surface area. A pair of divers can clean a midsize hull in a day. Propeller removal and repair usually follow a line strike or impact. The diver unbolts the prop, bags the fasteners, and sends it to the surface for the machine shop to true and repitch. The hull exam for commercial vessels follows 46 CFR 71.50-3, also known as UWILD. Keep in mind that a hull cleaning crew is not the same as an UWILD inspection team. Ask which one you need.
Dredging and Marine Salvage
Dredging is a production job. Hydraulic cutterhead dredges suck slurry through a pipeline; mechanical excavators and clamshells lift the bottom directly. The dive contractor is typically brought in for debris clearing, tool placement, and final bottom surveys. Dredging is priced by cubic yard, but mobilization is the largest variable. Marine salvage is different. It begins with an assessment of the casualty—a capsized barge, a sunk trawler, or an engine-room flood. Salvors work on Lloyd's Open Form or on a straight time-and-materials basis with a guaranteed maximum price. Underwater cutting, rigging, and lifting bags are the core tools. Most salvage work is irregular, which is why you see daily rates plus a salvage premium. Several large segments run in winter: lock dewatering, Great Lakes layup maintenance, Pacific Northwest estuary windows, and Gulf post-storm repair. That's why a seasoned contractor plans a year-round schedule.
Questions about underwater services
What qualifications should my commercial diving contractor have?
Commercial divers must work under OSHA 29 CFR 1910 Subpart T and follow the ADCI consensus standards. On a bridge inspection, the team leader must meet FHWA-NHI requirements under 23 CFR 650.311. Recreational scuba certification (PADI or any other agency) is not a commercial qualification. Ask for the contractor's ADCI certification and their specific experience on the structure you own.
How are underwater inspections scheduled, and how often?
The interval is dictated by your facility's regulatory program. Bridges are inspected on a set schedule per NBIS; underwater inspections may be up to 60 months for bridges with a low risk. Water storage tanks follow AWWA M42 intervals, typically every 3-5 years; 46 CFR 71.50-3 governs UWILD for commercial vessels. Your contractor can review your last inspection and recommend a date.
Can divers work near intakes, gates, or valves while water is flowing?
No. If a diver is close to any pressure differential, the water flow (delta P) can pin them to the structure and cause fatal injuries. The site must be positively isolated—valves closed, blank flanges installed, or the equipment locked out. This is not a routine operation; the dive plan will include a written rescue procedure.
How is underwater work priced?
The biggest cost is mobilization and the daily crew rate—typically a diver, a tender, and a surface operator. On top of that you add the barge or vessel, the compressor or dive system, and special tools like underwater welding or hydraulic equipment. Inspection work is usually per day; repair and construction is per linear foot, per pile, or per cubic yard. The contractor should provide a line-item quote after a dive survey.