Blunder Below is a 1942 animated short from Popeye the Sailor series. It is a typical war propaganda film of its time.
Popeye is in the navy and has trouble learning the ropes, but when the Japanese submarine emerges, he attacks it using his specialty which is of course spinach. Needless to say, I really liked that ending. Despite its poor taste, those action moments were so great and it was funny watching Popeye in this environment. The entire short is pretty slow and sometimes even dull, but that ending is great along with the final line. The beginning is also pretty amusing.
But it is a typical war entry meaning that it is not much of a Popeye short as it is a propaganda piece. And I really disliked the stereotypical portrayal of Japanese people with large teeth and squeaky voice. That was awful to witness, but expected from the 40s. But having in mind its theme, the film could have been much worse.