For underwater or below-floating-dock installations in commercial marinas, the recommended cable type must withstand continuous submersion, moisture, mechanical stress, UV exposure, and NEC marina-specific safety rules.
Here are the industry-standard cable types used under floating docks:
Best Cable Types for Underneath Floating Docks (Commercial Marinas)
Submersible Pump Waterproof Rubber Cable
1. Submersible Pump Cable (Waterproof Cable)
Use when the cable will be fully submerged underwater.
Rated for continuous submersion
Flexible thermoplastic or thermoset insulation (PVC, XLPE, EPR)
Common types include Pump Cable / Submersible Pump Wire
Often used for dock lighting and underwater power feeds
👉 Ideal if the cable must run underwater between dock sections.
2. Marine-Grade
what is soow cable used for
or SEOOW Cable (in conduit only)
Use only if installed inside watertight conduit.
Oil-resistant / water-resistant / flexible
600V rated
Durable for movement of floating docks
Cannot be used directly in water unless inside conduit
👉 Good for areas exposed to flexing, movement, or abrasion.
3. TC-ER Marine Cable (in conduit or protected locations)
Suitable for trays, docks, and exposed runs when not submerged.
Tray Cable – Exposed Run (ER) rating
UV resistant, sunlight resistant
Good for running under docks above waterline or inside protective raceways
👉 Works well for commercial dock power distribution.
4. UF-B or USE-2/RHH/RHW-2 (For underground → dock transition)
Not suitable underwater, but used:
From shore to gangway
Buried portions of the marina electrical system
👉 Use where the wiring comes from land to the start of the dock structure.
NEC Requirements to Consider (Important!)
The NEC (National Electrical Code) Article 555 – Marinas and Boatyards requires:
✔ Wiring must be “extra-hard usage”
Meaning SOOW, SEOOW, or better.
✔ No standard NM-B, THHN, Romex, or non-marine cables
✔ All dock wiring must be GFCI or GFPE protected
✔ All underwater wiring must be rated for submersion
✔ Must be installed in conduit where required and protected from physical damage
Recommended Cable for Most Commercial Marina Floating Docks
→ Submersible Pump Cable (directly submerged sections)
→ Marine SOOW/SEOOW Cable (flexible dock sections, inside conduit)
→ TC-ER Marine Cable (exposed but above-water sections)
This combination gives:
Waterproof performance
Flexibility for dock movement
Compliance with NEC 555
Long service life in harsh marine environments
