If encountered and hit by that on your boat, u can escape by making zig zag movements until you reach the shore where it cant hit you. Ive lost som boats for it then used this tecnique and never lost them again, remeber to repair boat after the hit, so u be ready for next encounter. Best way to avoid it is navigate near shores
It will attacks rafts so be carful coming across one on a boat.
Also the Alpha Albino Leedsichthys Will give you raw prime fish me when you scrape meat off of it, and killing it will give you The Captains Hat Skin