noun
diving beetle; Japanese predacious diving beetle
Refers to diving beetles in general, and specifically to Cybister japonicus, a large species found in Japan. Often kept as a pet by children.
子供の頃、田んぼでゲンゴロウを捕まえた。
When I was a child, I caught diving beetles in the rice paddies.
ゲンゴロウは水
Diving beetles eat small fish underwater.