1 Long Tom: All hands! Be boardin' yon enemy vessel!
1 Nazi Captain: Alles hände! Board die enemy vessel!
2 {The crews swap ships.}
3 Wendy: Now what, cap'n?
4 Long Tom: Just be givin' me a second here to be absorbin' this turn o' events...

I wasn't sure if U-boats were ever involved in boarding actions, so I did a search. Many of the top hits referred to the U-boat U-505, which was boarded and captured by an American crew of the USS Pillsbury in May 1944, although this happened after the German crew had already abandoned the ship.

The U-110 was also boarded in similar circumstances by a British crew in 1941, after the U-boat crew had abandoned ship.

I couldn't find any examples of U-boat crews boarding surface vessels, but then that was never intended to even remotely be their role in combat.

EDIT: Technically the Nazi Captain's opening sentence should, in the correct idiomatic translation, be "Alle Mann!" not "Alles hände!" Consider this just another example of the deliberately fractured German spoken by the Nazis in this comic.