There are generally three types of boat, in-land (used on lakes and rivers), in-shore (used closer to shore) and off-shore (into deeper waters and further out to sea). A rescue lifeboat is a boat designed with specialised features for searching for, rescuing and saving the lives of people in peril at sea or in estuaries.
and rescue lifeboats are typically vessels manned by volunteers, intended for quick dispatch, launch and transit to reach a ship or individuals in trouble at sea. Off-shore boats are referred to as ‘All-weather’ and generally have a range of 150–250 nautical miles. Characteristics such as capability to withstand heavy weather, fuel capacity, navigation and communication devices carried, vary with size.
A vessel and her crew can be used for operation out to, say, 20 nautical miles (37 km) away from a place of safe refuge, remaining at or on the scene to search for several hours, with fuel reserves sufficient for returning; operating in up to gale force sea conditions; in daylight, fog and darkness. A smaller IRB inshore rescue boat / ILB inshore life boat and her crew would not be able to withstand (or even survive) these conditions for long.