if tyson is son of Poseidon then why doesnt he use water powers like percy? And technically, aren't cyclops considered monsters, so he could come back if he were killed?

Well, I think only demigod children of Poseidon have water powers. Have آپ ever seen any other sons of Poseidon, Polyphemus یا Blackjack for example, controlling the water?
As to the monster thing, Kaylee, I guess you're right.

he can breath under water and ha can talk to water life and such. and yes he can come back but Percy is scared of loosing him because monsters can stay dead for a life time.

Good سوال i wonder that too آپ should look it up in the Greek myths