This is the first of Vito Scotti's two appearances as the Japanese soldier. His second appearance is later in the first season in the episode "Diogenes, Won't You Please Go Home."
You can see the water rise up through the sub when Gilligan submerges it with the top open. Obviously it was a turrent.
Skipper: Now, if you were a Japanese sailor, where would you be?
Gilligan: In Tokyo.
Skipper: I mean here on this island, Gilligan.
Gilligan: (looking at the sub) Somebody sure has terrible handwriting.
Skipper: Gilligan, it's Japanese.
Skipper: Where is everybody?
Gilligan: Out to lunch.
Skipper: Out to lunch?
Gilligan: The hard way.
Gilligan: The sea serpent ate Ginger.
Professor: Why did she scream?
Gilligan: Because it hurts.
Lovey: It sounded like Ginger.
Professor: But she's with Gilligan.
Lovey: Oh Professor, I refuse to listen to anything more. Gilligan's a very nice little boy.
Professor: I didn't mean it like that.
Theme of episode: Always listen to the boy who cries wolf, because one day he may be right.
Japan never made one man submarines. YES THEY DID!!! The first Japanese soldier captured after the attack on Pearl Harbor was from a beached one man sub. In fact there were several destroyed in that attack.
This was Vito Scotti's first appearance. He later would make two appearances as mad scientist Doctor Boris Balinkoff.