Cables for Marine, Offshore and Subsea Applications
Subsea cable is specified around two external forces: hydrostatic pressure that increases with depth, and the buoyancy the cable must have to behave predictably in the water column. An ROV tether that is positively buoyant floats and tangles; one that is neutrally buoyant follows the vehicle; one that is negatively buoyant drags on the seabed. Buoyancy is therefore an engineering specification, not a jacket preference.
Water blocking is the second defining property. A cable that lets water migrate along the core loses its electrical properties from the damaged point onward. Water-blocking tapes and fillers, plus armour where mechanical protection is needed, are standard in this sector.
What decides the cable in this application
Four factors do most of the work. Getting these right narrows the choice to a small number of constructions, and each one appears in the specification table of the cable type you select.
Buoyancy determines how the cable behaves in the water
Positive, neutral and negative buoyancy are three different products. A tether that is positively buoyant will rise and tangle around the vehicle, while a neutrally buoyant one follows it without either floating or dragging.
Hydrostatic pressure rises with depth
Where the cable runs deep, the construction has to resist pressure without deforming or letting water migrate along the core. Water-blocking elements and a pressure-resistant core are part of the specification.
Water migration destroys a cable from the damage point
Once water travels along a stranded conductor the electrical properties degrade along the whole length. Longitudinal water blocking is what confines the damage to the point of entry.
Mechanical protection for seabed and deck work
Cable that contacts the seabed, passes through a sheave, or is handled on deck needs armour or heavy sheathing. Interlocking armour is the usual answer where crush and abrasion protection is required.
Cable types for marine, offshore & subsea
14 constructions from the catalogue that suit this duty. Each links to its own page with the full specification table.
What we need to quote accurately
Send these six items and we can confirm a construction and price without a follow-up round. Both the contact page and every product page carry a form that accepts them, and you can attach a drawing or specification sheet directly.
- 1 Operating depth Maximum water depth — drives pressure and water-blocking requirements
- 2 Buoyancy requirement Positive, neutral or negative, and the tolerance acceptable
- 3 Cable function Power, fibre, signal, or a composite umbilical
- 4 Mechanical duty Seabed contact, sheave passage, deck handling, crush risk
- 5 Voltage and data requirement Voltage rating, data rate, fibre count if applicable
- 6 Standard required Marine or defence standard the project is specified against
Frequently asked questions
How do I choose between floating, neutrally buoyant and sinking cable?
From how the cable must behave in the water column. A surface-tethered cable that should not drag on the seabed is made positively buoyant; an ROV tether that must follow the vehicle without loading it is made neutrally buoyant. Tell us the depth and the vehicle behaviour and we will confirm the construction.
Why does water blocking matter so much in subsea cable?
Because damage at one point otherwise degrades the whole cable. Water migrates along stranded conductors and through fillers, so longitudinal water-blocking tapes and fillers confine the damage to the point of entry instead of letting it travel the full length.
When is interlocking armour needed?
Where the cable risks crush or abrasion — seabed contact, sheave passage, deck handling. Interlocking armour provides mechanical protection while keeping the cable flexible enough to run over a sheave.
Can power and fibre run in one subsea cable?
Yes, and composite umbilicals are common because they reduce the number of separate cables in the water. The specification then covers both the power rating and the fibre count and type, and the construction has to protect both.
Need the cable confirmed against your machine?
Send the duty, the environment and the electrical data. Our engineering team will confirm the construction, the standards it meets, and the price — including custom builds where a catalogue type does not fit.