vanguard (leading units of an army) / forward (player nearest to the opposing soccer team), lineman (playing position in football), or similar positions in tennis, volleyball, and other sports

(geometry) acute angle

electric ray

"to distinguish sour and sweet by biting": to be familiar with the ways of the world

水文学: hydrology

水素爆弾: a hydrogen bomb

降水量: precipitation, rainfall - (the amount of the rain that had fallen)

海水着: bathing suit

海水パンツ: swimming trunks

海水魚: saltwater fish