Sulfur goo and land fish

When a TNT sulfur cube explodes, it should drop "Sulfur Goo." Combine that with Redstone on a crafting table, and you get "Radioactive Goo." Slap that on any aquatic mob, and they will stop flailing wildly. They will have their own unique land animations, can move on land calmly or at all (looking at you, squids & nautili), and can survive on land indefinitely.