- The C2 version is amphibious. Their color is enhanced from the base genome, so they are typically brighter than the surrounding aquatic creatures. The strangest thing about them is they practically never sleep. They use the sprites of Bulbous Grendels and MerNorns. At one time, due to a crash, the C2 sea monsters were lost. But Grendel Man remade them, and gave them Scorpio Norn arms. This version never saw a public release.
- The C3/DS version is also amphibious, but has no tendency to stay in the water. They also have instincts to eat critters. They crawl on all fours all of their lives, too. They are peaceful and friendly unless smacked by another creature. Then depending on the type of creature, they either retreat or hit back. Most notably, they are expressive, even though the basis was the C3 Grendel Genome. They use the sprites of the Jungle Grendels, Maraquan Grendels, and the Gargoyle Norns.
- Version 1.4 of the C3/DS Sea Monsters use only C3 Grendel sprites and Maraquan Sprites, the color is a lighter blue, they return to water in order to breed, and are generally friendlier. They can be found here
Note: There is a spritemix called "Little Sea Monsters"; these are norns with maraquan tails and aqua legs that use the Aquanorn genome. They have no relation to the Sea Monster grendels.