I believe some sea creatures like the octopus might evolve into something really intelligent, it got the tentacles to create and form things and is a quite clever creature, if the humans didnt have the hands (especially the thump) we wouldnt have evolved the way we did, but will the tentacles be as importent for them as the hands where for us. As a sidenote intelligent life in water would look totally diffrent then in air, where fire meant hell of alot for us humans, what would sea creatures be able to control in a way that would help them advance further?
octopuses have developed other stuff like camouflage, fleeing using ink clouds, using seashells as shields, thier speed, strong tentacles with good grip, and a brain like no other in the sea, also dolphins are quite clever but needs something wich can hold things similar to a hand or tentacles
Also small insects like ants and bees are quite significant in the ways they "built" up and controll thier empires, the ant as an examble have farms in thier nests where they grow mushrooms and farm it, is things like that based on instinct? i would believe so, but still quite facinating.