There are over a hundred species of water beetles, however the diving beetles are large and easy to identify. This one is a Lesser Diving Beetle, as opposed to the Great Diving Beetle which is almost twice as large. The Lesser Diving Battle is nicely patterned and about 15mm long - best observed when it comes to the surface for air. This one was seen in the Lily Pond below the monument. The second photo shows the larval stage.