Amphitrite is one, Thetis another.
The whole gang is called nereids.
The Nereids were their daughters.
In ancinet Greek mythology, Nereus was the prophetic and shapeshifting "old man of the sea"; by his wife Doris, daughter of Oceanus and Tethys, he had fifty daughters called the Nereids. Nereus was son of Pontus and Gaea.
Nereids, daughters of Nereus, are the 50 sea nymphs. Some of these include Amphitrite, the wife of Poseidon and Thetis, the mother of Achilles. Other sea nymphs included the Atlantiades, daughters of Atlas, like Calypso, but the Nereids are the traditional "sea nymphs".
Nereids, see link below for a list of names.
Nereid's Roman name is Nerine. In mythology, Nereids are sea nymphs and daughters of the sea god Nereus. They are often associated with the Mediterranean Sea and are known for their beauty and kindness. Nerine embodies the characteristics of these sea deities in Roman mythology.