Just got back from Kauai. Snorkeling off the south shore at Poipu with the kids was great for seeing SPS & LPS. Even the estuaries were full of achilles tangs, convict tangs, yellow tangs & blennies, right there in tide pools at your feet with no escape... The reefs are better on the north shore but the waves & riptides there were killer, too strong for us. Kauai is one of the oldest Hawaiian islands so i fugure the reefs are mature, plus fewer people than the others.