Heeia State Park is located on Oahu's eastern shore, right on the popular Kaneohe Bay. The park covers about 18.5 acres, with one side on Kaneohe Bay and not far from the town of Kaneohe. It's between the Heeia Fish Pond and a small harbor called He'eia Kea. There are picnic facilities, including some with covers, and walking trails.
From Heeia State Park, you can see not only Kaneohe Bay but also the Koolau mountains. There are sometimes walking tours available, as well as kayaking and snorkeling tours and occasionally classes on canoe building.
At low tide, a sandbar in Kaneohe Bay becomes accessible by kayak—that's one of the most popular things to do in this part of the island.