[1] The Inshore boat was designed at Atlantic College in South Wales, the birthplace of the RIB, after which the craft is named.

The college was also one of nine locations where the RNLI first established lifeboat stations using smaller inshore watercraft.

[1][3] The Atlantic 21 can be launched from a davit, carriage or floating boathouse depending on the location of the station and the available facilities.

The lifeboat is a rigid inflatable boat (RIB), with the hull constructed of Fibre-reinforced plastic, subdivided into water-tight compartments, and manufactured at Halmatic Ltd. of Havant.

The boats are then fitted out at the RNLI Inshore Lifeboat Centre in at East Cowes, Isle of Wight.