I raided a base that had so much stuff that I needed to use a boat to get all of it back to my base (herbivore island). As I reached my base I was attacked by one of these whales and it destroyed my boat and with it all the wooden storages. I dived and dived by I never saw my loot again.
That was the last time I ever made a base on herbivore island.
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