The Hammar H2O R hydrostatic release unit is designed for liferafts from 6 to 150 persons. The H2O R consists of a double looped white rope line, a release mechanism and a Red Weak Link breaking strength 2.2 ± 0.4 kN).

The strong white rope is secured to the deck or liferaft cradle and attached to the liferaft lashing with a sliphook. If the ship sinks, the water pressure will (within 4 metres) activate the sharp knife which cuts the white rope and the liferaft will float free. As the ship sinks, the liferaft painter line will be stretched and the liferaft starts to inflate. The Red Weak Link breaks and survivors can board the floating liferaft.

The H2O R is made of glassfibre reinforced nylon, which means it won't rust. The H2O R needs no annual service maintenance or spare parts, however it must be replaced after 2 years. H2O's must be marked with its expiry date in order to be approved. Each has its own individual serial number.