I gotta say "cast on" instead of "cast off"?

Well now, themilum. What are you gonna "cast off" when you say "cast off"?

If you "cast off" your lines you won't have any lines to tie up with when you return. And you won't be casting Tramp overboard if your buddy Bobby has anything to say about it.

"Cast off" the skipper commanded
To a novice since his ship was short-handed
Into the drink
Went the lines in a blink
"Keelhaul him!", the crew countermanded.

P.S. I've got it, themilum. You can say "Shove off".