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.
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Rated for continuous submersion
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Flexible thermoplastic or thermoset insulation (PVC, XLPE, EPR)
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Common types include Pump Cable / Submersible Pump Wire
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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.
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Oil-resistant / water-resistant / flexible
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600V rated
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Durable for movement of floating docks
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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.
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Tray Cable – Exposed Run (ER) rating
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UV resistant, sunlight resistant
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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:
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From shore to gangway
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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:
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Waterproof performance
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Flexibility for dock movement
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Compliance with NEC 555
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Long service life in harsh marine environments
