Jim Goodwin (Helmsman's voice)
Although the Flying Sub is on the sea bed, when Crane goes through the escape hatch, stock footage makes him appear to emerge into open water, when the sea bed should have been inches away.
This is the second sighting of a giant Portugese Man o' War, the first being from "Mutiny" in the first season. Unlike the first, this one has the ability to throw electrical charges.
They use stock footage showing a camera angle from inside a toothed mouth (used in "Leviathan" where the diver was eaten by a giant sawfish) but man 'o wars do not have mouths as such.
(The man 'o war has been jolted with a reflection of its own discharge)
Kowalski: Hey, that'll teach that, that oversized storage battery not to fool around with us!