What's the name of this 90's anime movie?

OK, this has gnawed on me since I was 6 and now I'm 15. I rented this anime movie from Blockbuster right after I rented Kiki's Delivery Service and can't remember the frickin name of it. From what I remember it was about this boy and he was near the sea. He swam with dolphins at some point and he went into this cove also. And NO! It isn't Free Willy or Flipper or ANYTHING like that! It also isn't in black and white, it was very colorful and like I said was in the 90's. Please help me!