The movie 'the beach' made Leh is Maya Bay in Koh Phi Phi famous. It is now Phi Phi's most frequented snorkling water and is an amazing spot to scuba dive too.
It's possible to dive the walls outside of the bay to the south and the north with the latter offering more of interest.
The awesome island walls that look so beautiful above the water, are just stunning below and in many places huge boulders have fallen and fused together to create exciting swim-throughs filled with glassfish. A good dive light is useful for looking into and under rocks in search of critters.
This site has mainly hard coral cover which is not as prolific as at other Phi Phi dive sites but is still host to a multitude of reef fish including wrasse, rock groupers, snappers, bannerfish, oriental sweetlips and moorish idols. At the very northern edge of the wall schools of black tips reef sharks circle constantly. And you may be lucky enough to see leopard sharks here;
Maya Wall