The amount of tow cable exposed to part or all of the water column and potentially affected by drag forces. When towing sonar with small amounts of cable in the water, ship manoeuvres are simpler and towfish behaviour is easily controlled. As the water depth (and in-water-cable) increase, cable catanary and towfish height become important parametres. Also, the vessel becomes more restricted in its movements. This complicates manoeuvrability when trying to avoid towfish-seafloor collisions and ship-towcable accidents.