Insects and Spiders - Giant Water Scavenger Beetle
Hydrophilus triangularis

Water scavenger beetles are a family of beetles that are mostly aquatic. They are not scavengers in the sense that they eat only dead wildlife or plants. While the do scavenge on dead material some, they also feed on living plants and organisms. In their larval stage, they are entirely predatory. I found this beetle near the lake, upside down, and struggling intermittently to right itself.

The beetle seemed to have a dent on its upper side. It had a hard time moving even after I righted it, so it may also have been missing legs.