All I can remember is that there was a pink sea monster who had just been hatched and she (or he? I dunno, I guess it was a girl, I'm going by memory instead of just re-looking it up) had these two kid friends and they were on a beach. And they had to save something. And deep below the sea was this snobby blue-haired mermaid princess who wanted nothing to do with it, but the octopus wearing glasses kept telling her that it was in her best interests to help Serendipity.
I'm probably way off, but I do remember that the characters looked NOTHING like they do on the cover, and I did read somewhere that this was true.
There's another anime from my childhood called Honey Honey that I haven't been able to find, and for some reason I remember the entire plot and most of the dialogue. But in any case, Serendipity was much better.
And also, because karma_fucked said she wanted me to post this, I found Hyde. Here he is: