Have you ever wondered what would happen if Submarimon was attacked while Cody was inside him, and he dedigivolved? Would Cody be stuck in the shell? He'd be all "Someone help!" and Armadillomon would be all "Cody, I can hear ya but I can't see ya!"
DYNAMIC RELOCATION OF PRECEDING ENGLISH LANGUAGE IN ANCII-FORMAT BINARY CODE.
He'd probably just get thrown out, start choking in the water, and then Deus Ex Machina would kick in. He'd either swim to the surface or be picked up by some other digimon or find an underwater cave or air supply.