Basking shark

Basking sharks are generally solitary or gather in small schools.

An excerpt from the article 16 facts about Basking shark

At times, there can be an aggregation of more than 100 sharks. They move slowly, filtering plankton, extending their dorsal fin out of the water and even flipping their bellies. These fish swim at a speed of about 3.7 km/h and do not tend to swim away from approaching vessels.