The pirates show the diving suit to Kiljaos, which they previously stole right under his nose in Karamador: Fairy of Tasku. They stole it because it was one of it's kind and it's owner, mayor Corbalt, didn't have it's design plans, and also have made new copies of it that fit better on animals. With these diving suits they are going to retrieve a pile of treasure undersea, but it's guarded by a big sea monster. So Sir Kiljaos the lion paladin is b̶l̶a̶c̶k̶m̶a̶i̶l̶e̶d̶ asked to join them to retrieve this treasure in case if it's impossible to sneak past the sea monster and they have to fight it.

The diving suit seen here is based on the world's oldest diving suit, made in the 18th century, nicknamed "The Old Gentleman". It's kept in the museum of my hometown Raahe, here in Finland.

Also, these anthro animals are indeed known as Anhini animals or just Anhinis in Karamadors.