I have no doubt at all that the words have been made up for the program. None. Nada.

What some hear as "churning brine" might equally be "turning bright."
"Dash the spear and watch him float" is a possibility, but "dash" sounds odd. (I don't hear anything like "Land.") I think "float" makes more sense than "bloat."

Possibly the final words are "this dory-line," not that it makes much sense. It could even be "The story line"! Or something else. "The overtime is surely thine" sounds impossible to me. It *could* mean (in theory) "You'll surely be paid for your overtime work," but it would be a *very* weird way of saying it, like mixing Shakespeare with Steinbeck.

Maybe the lyrics were adlibbed by somebody who was not quite fluent in either whaling or 19th Century English!