I have five points like a certain shape I live underwater and not the surface Unlike my name I’m related to sand dollars

Can you feel the claws digging into your tongue? Oh wait you can't talk right now...

I move in deep cover, work in the dark. Espionage, or a beautiful mark?

I'm massive and gray, with a memory so bright, My tusks are my pride, in the savannah's light, I roam with my herd, with a trumpeting sound, My wrinkled skin's tough, but my heart's soft ground.

Two blades you should have with me to guide me, enclosed you'll feel at home. safely through rapids, don't capsize. I'm a simple aquatic palindrome.