I don't know about seeing dolphins while physically standing on the shore of a Marriott resort, but dolphins, whales, and even my favorites - monk seals - are all over the place in Kauai. (Well, the seals are very rare, but dolphins and whales are every-freaking-where.) Several dolphin species - spinners and some bigger ones, shoot me for forgetting the name...

Take your pick of the Marriotts there...the animals can be seen by either boat or chopper.