Hawaiian Trough the Hawaiian Arch. The Hawaiian Arch extends about 200 meters above the surrounding ocean floor, and contains tilted coral reefs. The coral reefs in the Hawaiian Tough are described as mesophotic coral ecosystems, which can be found between 100 and 500 feet below sea level. 43 percent of fish species documented at the mesophotic reefs are unique to the Hawaiian Islands. At Maui’s ‘Au’au channel the largest uninterrupted mesophotic coral ecosystem was discovered, with an area larger than 3 square miles. These reefs contained many stony, reef building coral that belong to the genus Leptoseris, which are adapted for deep
Channels of the Hawaiian Islands north, and Kahoʻolawe to the south. The depth of the channel reaches , and its width is . ʻAuʻau channel is a whale-watching center in the Hawaiian Islands. Humpback whales migrate approximately 3,500 miles (5600 km) from Alaskan waters each autumn and spend the northern hemisphere winter months in the protected waters of the channel. ʻAuʻau translates to "to take a bath" referring to its calm bath-like conditions. The middle of the ʻAuʻau channel off Lahaina is known as the Lahaina Roads. Once filled with whalers when Lahaina was a capital for that industry, Lahaina Roads were later adopted as