I'm not sure what the stats page is either... lol

Of the 23 current Aquatic Petpets, we're missing 7 (which are painted combinations we've yet to get the ID for). The rest are unreleased combinations/petpets and 1 is the Snow Crabula which is announced but not yet paintable.

This is pretty common throughout the database, we have quite a bit of items in there Neopets has never announced in the news (and probably will never), as well as those they've yet to activate.