Sand dollars

We were out with the boat late in the afternoon. It was a beautiful day.
We drove into shallow water to look at the Sand dollars.
I found this text on the internet:

A sand dollar shell looks sort of like a round white coin, which is where it gets its name. When you see a sand dollar that's washed up on the beach, it usually appears to be a round, white circular disk, typically one inch to four inches in diameter. When they're alilve they're actually a dark color, covered with short dark spines that look almost like fur. These spines are moveable, and the sand dollar uses them both to move around on sea bottom and to push small pieces of food to its mouth.