Let's come up with an amphibian race!

What’s the difficulty here? These are different seas. One is a sea, and the other is a sea. We can make it so that the density of the water in the underground sea is higher, allowing the Garray to move across it as if it were land, while only Krakens can swim freely in the surface sea; the surface sea is too thin for others, and they are pulled back down into the depths. Or, we can make it so that the Garray have lived in the darkness of the underground sea for so long that they need protection from sunlight when moving on the surface (including in the water) – a ship.