There are two types of merpeople. Mermaids and Sirens Their customs and language are different. The Mermaids use words while the Sirens use sound.

Izuku has just gotten cast out of his pod because he refuses to bow to Bakugo. His tears fall as he swims into unknown territory of the deep. He senses someone following him. He swims even faster, knowing he has entered Siren territory. His body trembles as he swims, tears falling faster.