We stayed at the El Nido lodge and were very comfortable there but there are tons of places to choose from, probably 10-15 within walking distance of this beach.

It's not bad, so so. There are better places further down the beach. The coral, as in many places has been somewhat abused and stepped on. This of course leads to poor wildlife and dead coral in places. Really it depends on your experience and what good places you have snorkeled before. Bringing your own gear is a better idea though as the gear rental places were somewhat poor.. One snorkel set fell apart on me.

Yes, playa negra is perfectly sandy and no coral near the shore. Playa chiquita is also sandy but the sand isn’t as fine as playa negra.

You don’t have to travel far, if you stay at Banana azul they take care of all arrangements and provide shuttles.