(figuratively) being carefree and unaware of an imminent danger

(idiomatic) "a fish who's found water" → In one's element, a duck to water.

Alternative spelling of 鱛

a Japanese giant salamander

(astrology) Pisces

a barracuda

a fourspine sculpin (species Cottus kazika); very similar to the kajika (see below), but larger

(rare) a fourspine sculpin (species Cottus kazika); very similar to the kajika (see below), but larger

a Japanese fluvial sculpin (species Cottus pollux); very similar to the kamakiri (see above), but smaller

a Japanese fluvial sculpin (species Cottus pollux), more commonly known as 鰍 (kajika)