North of Honolulu and Haleiwa at Laniakea Beach, the snorkeling at Turtle Beach is, of course, popular for its regular population of green sea turtles. They are often found resting on the beach and there are usually a half dozen or more feeding in the waters of the protected cove. The snorkeling at Laniakea Beach is not known for exceptional water clarity. In fact, many consider the water to be a little cloudy.
The cove needs calm seas for snorkeling. Matter of fact, the cove is usually signed "no swimming" and "rip current" from December through early May. When signed, the rip current can be unusually strong having surprise many intermediate snorkelers.
To reach the snorkeling at Turtle Beach from Haleiwa, head north on Kamehameha Highway for 1.75 miles to Laniakea Beach. There is a dirt turnout parking area across from the beach. To reach the best snorkeling on Oahu by air, you will need to fly into Honolulu International Airport (HNL) which is located just on the west side of Honolulu. There are direct flights into Honolulu from the US, Australia, New Zealand, American Samoa, Tahiti, Japan and Fiji. In addition, there are inter-island flights to all the main Hawaiian Islands. There is good snorkeling on Oahu year-round. But, the conditions very around the island depending upon time of year due to winds and currents. The north shore snorkeling dives are best from June through September and are usually closed out the rest of the year due to high surf. The south shore dive sites are best from November through May. The main exception is Hanauma Bay, which tends to be good year-round since it is very protected.
Overall, Turtle Beach is the 17th most popular snorkel dive spot of all 23 snorkeling dives in Oahu.