Sediment

• Layers on his body fluctuate, they don't have to be exact
• Sometimes you can see fossils and other critters mixed in the soil layers

Sediment is a curious loner who spends his time adding to his massive collection of bones, scales, shells, and general ocean debris. He is single minded in his goal to find more cool stuff, and goes on long expeditions around the seabed to add to his collection, often storing pieces in his body for transport since he lacks hands or bags. While he is friendly, he is skittish and avoids human contact, preferring to keep to himself. Due to the fact he's made of sand and isn't food- sea creatures typically ignore or dismiss him as some strange moving rock (To his benefit).

While very nosy and filled with wonder at the world above, he's smart enough to keep a safe distance and watch from below the waves. He doesn't have enough desire to engage so as to put himself at any risk. 

He feels aimless and purposeless since his creator passed away (simply of age- living sand lives longer than flesh, of course). He continues his original mission mechanically, simply because he doesn't know what else to do with his time. While he isn't stupid- he isn't a deep thinker and has little desire to deeply evaluate and reconsider something as ambiguous as his purpose for life. 

Sediment is a creature that lives at the bottom of the sea, gathering the bones that drift to the sand at the bottom of the waves. It is capable of breathing water and on land. It was created aoes ago by a sorverer that wanted to learn more about the sea, and thus created this entity that would go to the sea and bring back samples of fossils and other non-dangerous life.  The creation outlived its master, so now Sediment wanders aimlessly, collecting its bones in a massive boneyard its formed in an unknown location at the bottom of the sea.

While it does not typically engage with the world above- that continues on as it's wont to do, it occasionally appears or is seen in very unusual meetings. Mostly, when it snatches bones right out from scientists or other researchers who suddenly find an odd cat-creature under the sea making off with their things. 

It seems to aimlessly continue the one purpose it knew and has always known, without really understanding or knowing why, or knowing where to go from here.