It is silent except for the fish munching coral. A distinctive chewing sound. This is difficult to do. Sand dollars are white, they blend in with the sand are therefore hard to see. I wore a mask for this, no snorkel.
Sand dollars are very fragile.
If you get too excited about finding one and grasp it too tightly, it breaks. I broke all mine. I went snorkeling 2 other times this week, both Club Med trips, so they were free but you had to buddy up. On the first of these trips, to Whitehouse Reef, I didn't hear the part about buddying up. I went alone and stalked a Parrot Fish.