Dytiscid and Hydrophilid beetles are insects. About a million insect species have been discovered and researchers estimate that at least two million exist. The number of insect species on Earth is greater than the total of all other animal species combined.
Most insect species live on land. There are only about 20,000 species of insects that spend part or all of their lives in the water. That means that only 2% of insects live in aquatic environments! Most of them must have clean water environments to survive.