four-eyed fish
Refers to fish of the genus Anableps, known for their divided eyes that allow them to see above and below water simultaneously.
The four-eyed fish can see above and below the water surface at the same time.
Kanji spelling is rare and may not be widely recognized; the katakana form is preferred.
From 四つ (yotsu, 'four') + 目 (me, 'eye') + 魚 (uo, 'fish'), literally 'four-eyed fish'. The exact historical derivation is uncertain, but the name directly describes the fish's distinctive eyes.