The meaning of lifeboat described here is a boat designed to save the lives of people in trouble at sea. This term is predominantly used in the United Kingdom and Ireland, and may refer to special shore-based vessels manned by volunteers, designed to quickly reach a ship or individuals in trouble at sea. Lifeboats may be rigid or inflatable vessels.

Modern motor life boats (MLB) originated as life boats that had been modified with the addition of an engine and provided more power to get in and out of the swell area inside the surf. They can be launched from shore in any weather and perform rescues further distances out. Older lifeboats relied on sails and oars, which are slower and dependent on wind conditions or manpower. Both types remain in use. All lifeboats of this type generally have modern electronic devices such as radios and radar to help locate the party in distress and carry medical and food supplies for the survivors. The MLB was initially developed by the United States Life Saving Service in 1899, of which models derived from this hull design remained in use until 1987. The United States Life Saving Service later would become the United States Coast Guard and continue in its original mission of saving lives.

The Royal National Lifeboat Institution (or RNLI) maintains lifeboats around the coasts of the United Kingdom and Republic of Ireland, manned by unpaid volunteers, many part-time, with equipment funded through voluntary donation. Their stations operate Inshore and offshore ("All Weather") lifeboats. Most Scandinavian countries also have volunteer lifeboat societies. The local branch of a society generally schedules practices, maintains a lifeboat and shed, and is contacted by commercial marine radio operators when a rescue is needed.

In Australasia, surf lifesaving clubs operate inflatable rescue boats (IRB) for in-shore rescues of swimmers and surfers. These boats are best typified by the rubber Zodiac and are powered by an outboard motor. The rescue personnel wear wet suits.

The Rigid Hulled Inflatable boat (RIB) is now seen as the best type of craft for in-shore rescues as they are less likely to be tipped over by the wind or breakers. Specially designed jet rescue boats have also been used successfully. Unlike ordinary pleasure craft, these small to medium sized rescue craft often have very low freeboard so that victims can be taken aboard without lifting. This means that the boats are designed to operate with water inside the boat hull and rely on flotation tanks rather than hull displacement to stay afloat and upright.

Lifeboats are also operated inland at specific events; organizations such as the Royal Life Saving Society (RLSS UK) provide coverage of rivers, lakes and such like.