Seaplents which came to the Irinya Islands lost their flying ability and started to lay at the beach instead of flying around. This way, they could escape the Lurking Snatch. They also grew bigger, so that they won't be hunted by lizardworms. Their only predator is the snark. For the amphibious way of living, their wings evolved into flippers, and their little stumps became stronger, so that they can crawl over the beach. The breath hole is on a backfin now.