What kinds of animals usually live in areas often reperesented by blue on a map?

Fish, whales, dolphins, seals, sea lions depending on what area of the map you mean is blue. If it's the ocean it varies a lot from the ponds and rivers and lakes.

Also algae and water plants grow in ponds.

Crustaceans such as crabs and lobsters also live in the ocean. Some lobsters can be freshwater whilst others are saltwater.