Fathom ROV Tether (ROV-ready)


This professional-grade neutrally buoyant tether combines rugged strength and durability with high-performance electrical characteristics for wide-ranging ROV and subsea applications.

The new R2 version of the tether has a polyurethane jacket for improved flexibility and better adhesion to potting materials. Comes with pre-installed Binder 770 connector and cable penetrator.

HS Code: 8544.11.00.30

Product Description

The Fathom Tether is a high quality tether cable designed specifically for ROVs and other subsea applications. It is neutrally buoyant, has 350 lb breaking strength, and is embedded with water-blocking fibers to seal any leaks. The tether has a diameter of 7.6mm and is slimmer than the vast majority of comparable ROV tethers.

The tether carries four unshielded twisted pairs (UTP) of 26AWG wire. These pairs are colored and arranged in the same fashion as a Cat5 networking cable including cross-talk resistance. A pre-installed Binder 770 plug makes it easy to connect to the FXTI and Fathom Spool. A cable penetrator is installed at the other end to interface with the BlueROV2 or any of our watertight enclosures.

The core of the cable contains Kevlar strands for strength and Dacron fibers for space filling. Both fibers are impregnated with waterblocking compound to block any leaks caused by nicks or rips in the cable. The high-visibility yellow polyurethane foam jacket resists abrasion and provides neutral buoyancy.

The stiffness of the cable is designed to be flexible enough to give plenty of freedom to your ROV, but stiff enough that it does not become tangled easily. Due to the polyurethane jacket in the new version, the tether is more flexible than the original version.

The capabilities of this tether are meant to provide design flexibility and a wide variety of uses. Pololu carries the 3 position 0.1” (2.54mm) Crimp Connector Housings and male crimp pins that may be used for connecting your own devices to the spare tether terminations.

We also have this cable available by the meter with no terminations at either end.


  • 1 x Tether Cable with Binder 770 Plug and cable penetrator (choose length above)
  • 1 x Header pin to ferrule adapter to connect to Fathom-X
  • 1 x Cable Thimble
  • 5 x 8.5″ high-strength zip ties to secure the thimble


Tether Diameter7.6 mm0.30 in
Weight0.043 kg/m0.0287 lb/ft
Buoyancy in FreshwaterNeutral
Buoyancy in SaltwaterSlightly Positive
Wire Gauge0.14 mm226 AWG
Working Strength35 kgf80 lb
Breaking Strength155 kgf350 lb
Minimum Working Bend Diameter75 mm3 in
DC Resistance @ 20°C0.0386 Ω/ft0.127 Ω/m
Insulation Resistance @ 500 VDC> 500 MΩ/kft> 1640 MΩ/km
Voltage Rating300 VDC


PairWireColorBinder Connector Pin #
Pair 1Wire 1Blue/White1
Wire 2Blue2
Pair 2Wire 1Orange/White3
Wire 2Orange4
Pair 3Wire 1Green/White5
Wire 2Green6
Pair 4Wire 1Brown/White7
Wire 2Brown8

Cross Section

Revision History

7 August 2018

  • R2 – Update to new construction with polyurethane foam jacket

Quick Start

1. Install the cable penetrator on a watertight enclosure end-cap, such as the back of the BlueROV2.

2. Firmly attach the tether to your vehicle by following the thimble strain relief tutorial or some other method that prevents the tether from pulling directly on the tether penetrator. The tether can twist the penetrator loose if you do not provide strain relief.


Thimble use with Fathom Tether

Learn how to securely attach the Fathom Tether to a subsea vehicle!


Blue Robotics Forum – Product Support