The first Motor Landing Craft appeared in 1926, and only about nine were built through 1938. Their shallow-water role encouraged waterjet propulsion because exposed propellers could be damaged or fouled during beaching. A nominal top speed of five to six knots generally became about four and a half knots in practice, compared with about seven and a half knots attainable from comparable power through a propeller. That three-knot penalty mattered on the approach to a defended beach. The boats grew from about 16 to 20 tons, drew four and a half feet, and used Hotchkiss petrol engines. Some later craft received a different petrol engine, and bulletproof protection had been added to the steering shelter by 1936.
Chapter · 18:21-20:26
The 1926 Motor Landing Craft tested waterjet propulsion
Britain's small interwar MLC series used waterjets to reduce the risk of beach damage, but the choice carried a serious speed penalty compared with propeller propulsion.