Chapter 7-poseidon, sea deities, group divinities and monsters. Poseidon, best known as the great god of waters in general and of the sea in particular was not the first of such divinity. Pontus (the sea) was produced by ge in the initial stages of creation and two of the titans, oceanus and tethys bore thousands of children, the oceanids. Pontus mated with his mother ge and begat nereus who was gentle, wise, and old man of the sea with the gift of prophecy. Nereus in turn united with doris (an oceanid) who bore him 50 daughters, the nereids, three of them being thetis, galatea and amphitrite. When zeus refused to marry thetis because she was destined to bear a son mightier than his father, she married a mortal man, peleus and gave birth to achilles. Galatea, another nereid was loved by the cyclops polyphemus, a son of poseidon.