Turtle Bay occupies Kuilima Point, the blunt headland where Oʻahu's north shore turns the corner towards the windward side, and it is the only large resort on this coast. That fact shapes the whole northern end of the island: everything from Haleʻiwa to Kahuku is houses, beaches and food trucks, and then there is this, a very large landholding with hotel rooms, two golf courses, stables, restaurants and a considerable amount of shoreline.
The part most visitors do not realise is that the shoreline is not private. Hawaiʻi law makes beaches public to the upper reach of the wash of the waves, and developments of this size provide marked public access and a limited number of public parking stalls. You do not need to be a guest to use Kuilima Cove, walk the point, or reach Kawela Bay. You do need to arrive early enough to park, because the public stalls are finite and they go.
Kuilima Cove is the reason to come. It is a small bay held behind a reef that breaks the swell offshore, which makes it one of the very few places on the North Shore where swimming and easy snorkelling are realistic through the winter. The water is shallow, the entry is sand, and there are fish on the reef at the mouth. For a family staying up the coast in January, this and Haleʻiwa Beach Park are the list.
The point itself carries a network of paved and unpaved trails used by walkers and cyclists, running out around the headland with the ocean on three sides and no development in view for stretches of it. Kawela Bay, west of the resort, is quieter again: an ironwood and banyan grove behind a sheltered bay, reached on foot, and familiar to a lot of people from films shot on this coast without their ever having known where it was.
Whales pass offshore in the northern winter. Monk seals occasionally haul out on these beaches, in which case the sand around them is theirs.