This gigantic fish is so slow and easy-going that seaweed, barnacles and even a treasure chest and a few shipwreck parts have accumulated on its back when folks have mistook him to be a small island. He is absolutely huge, and usually hangs out between Tortuga and Devil's Anvil and the Privateering arena, but can also be found anywhere.
Mossy's sheer size makes him easy to hold onto, but he also takes much longer to wear out and bring in. You can haul some fish up at 30ft or even 50ft, but you have to reel Mossy all the way in to 0 ft. So, be prepared for a long fight. Many pirates find the struggle stage of this fish very tough so be warned. Mossy's scales pay 1,500 gold pieces when you bring him inland.