No one knows exactly when humpback whales first began wintering in the warm, shallow waters around the Hawaiian Islands. Narrative reports from whalers document the appearance of these majestic giants in Hawaii in the 1840s, but little evidence substantiates an earlier presence. But arrive they did, and today the waters around the main Hawaiian Islands of Kauai, Oahu, Hawaii, Maui, Molokai, Lanai and Kaho'olawe constitute one of the world's most important North Pacific humpback whale (Megaptera novaeangliae) habitats and the only place in the U.S. where humpbacks reproduce. Scientists estimate that two-thirds of the entire North Pacific humpback whale population (approximately 10,000 whales) migrate to Hawaiian waters to breed, calve and nurse their young. The Hawaiian Islands Humpback Whale National Marine Sanctuary also provides opportunities for surfing, diving and snorkeling.