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Ah... Ah, uwahhhhh, erg, glrk
Technically, "deta" means "get out" or "leave". But, the captain is screaming this as he's trying to escape, so I used the Monty Python "run away" reference.
Forgive me, Captain.
"waruku omou na" is generally translated by scanilators as "don't think badly of me", and that's the literal meaning. But, "forgive me" is a more common phrase in English with the same nuance, so that's what I used.
おい なんだ あいつは。
Hey, what is that?
Isn't it a movie vampire?
Technically, I should have said "movie Dracula". But, Tezuka is using the word "Dracula" interchangeably with "vampire" and the Japanese "blood sucking demon", and "movie vampire" seems to make a little more sense in English.
Who let that on the ship!
It's no joke, that's a real blood sucker!
Generally "joudan jai nai" gets treated as "no kidding", "no fooling" or "don't joke". In this specific case, the crew member is realizing that Dracula is the real thing rather than a prank, so I used "It's no joke" to convey that sensation.
It's already got the Captain and First Mate!
ヒヒヒヒッ ウヒヒヒヒャ くしゅぐったい
Hee hee hee... it, it tickles.