that would be immediately an s-tier defensive baby even better than dry baby; immune to explosions seems a bit ridiculous, maybe takes 50% of max hp from them, as for sperm whales they should still 100% be able to eat it no problem, and even with just being immune to pushback that makes him way more worth than 100 hearts, maybe 150-175 unless it's got a recharge that's as slow as an active item