What's This?
Do you see the mud circle? It is the muddy area on the water's surface left by a whale that is "snacking." Whales feed by gulping mouthfuls of sand and sediment from the bottom and squirting it out through their baleen. Any food gets trapped and swallowed.

The bottom sediment of the nursery lagoons in Mexico has very little whale food. However, the water is rich in plankton and algae. One type of algae is like cotton in texture. Scientist Dr. Swartz suggests this algae gets stuck on the whales' baleen, so maybe they are taking mouthfuls of sand and sediment to clean their baleen. The mud circle rises as they squirt out the mouthful of sediment.
—Caroline Armon, Guide/Naturalist

Courtesy of Caroline Armon

Mud circle indicates gray whale feeding activity