"A very large sea turtle, it's a giant sea monster with a landscape on the ridge of its back, so huge that it is often mistaken for an island and appears with palms and greenery.

I would be interested in other "sea monsters", they would of course need to be integrated into the story - a fight between different sea monsters would also be great, where you are suddenly in the middle of the fight with your own ship (like when the Kraken appears)"