Hi pword,
actually I always try and spend the last day snorkelling at that house reef - departing flight time permitting! On the 4 occasions I've been able to spend a day at PPR, it never seemed crowded, and you can certainly snorkel on your own no problem. There's a rope that links to a small swim platform several hundred metres out, and there aren't any boats between that and the beach. You probably wouldn't want to go beyond that rope. Apart from the giant clams, there are quite a lot of small colourful fish, and I've even seen a krait, calmly hunting and completely ignoring me for 20 minutes or so. The vis. is perfect. In the shallows I spent ages watching one of those fish/shrimp combos, where one keeps the hole in the sand clean and the other keeps watch. After a week's liveaboard diving with sharks and mantas it's obviously a bit gentle, but it's a very very nice way to relax before the 24 hour flight back to Europe!
Cheers,
Matthew