David is an odd fella. That being said the animal he wanted to be turned into was a lobster. Meaning he knows about sea creatures.
Before bringing her to the transformation room, the narrarator states that he wanted to kick her in the stomach and then stab her but didn't because she wouldn't feel any of it being tranqualized.
He turned her into a sea louse. The female sea louse is abducted by the male, then graped, graped by having her stomach punctured by the male. She will then be impregnated and while the babies mature inside of her they EAT HER ALIVE.
So yeah. This would be the kind of revenge he would love for her to get.