why, if the fish jumps up into the air, will it not be able to dive deep to die?

I don't have the text in front of me, but I know that the fish needs to jump in order to take in air, without enough air he cannot dive deeply. The man doesn't want to the fish to jump or to die.......... he wants him to circle so he can physically wear him out.

Okay, I found the entire quote on page 24, but I couldn't tell you why "filling the sacks along his backbone with air" would keep the fish from diving deep to die. Leave your other capsule open so someone else can chime in.........