A Japanese man sent on a mission in a submarine washes up on an American beach after his submarine breaks (can’t remember how). And there are three American (12-ish I believe) that find him and one of the boys is American/Japanese so they help him and keep him hidden from the authorities. They have a hideout in an old building which is by the sea/a river and I’m pretty sure the boys teach the Japanese man how to swim (or the other way around). Please help me find this movie!!