You will go sliding backwards on the ice or overboard the edge of the raft, with your dislocated shoulder. But you will really move backwards fast if you are in a place with no friction. Like, say, in space. So a rocket engine is just a way to fire some "reaction mass" (propellant...
You’d think a man could carry oxygen for a month, especially out in space where mass has no weight, or on the Moon where three pounds weigh only half a pound. Well, that’s okay for space stations or ships or frogmen; they run air through soda lime to take out carbon dioxide, ...