backswimmer

Noun

Any of various aquatic insects, of the family Notonectidae, that swim on their backs.

Japanese Meaning

背泳虫：水面上を背中を下に向けた状態で泳ぐことが特徴の、Notonectidae科に属する水生昆虫。

At dusk, the backswimmer darted beneath the lily pads, its long legs propelling it as though it were paddling.

夕暮れ、背面で泳ぐ水生昆虫が睡蓮の葉の下へと素早く進み、長い脚を櫂のように動かしていた。

Sense（1）

Any of various aquatic insects, of the family Notonectidae, that swim on their backs.

backswimmers

（ plural ）