With roughly 266 miles of coastline and an area twice the size of all the other Hawaiian Islands put together, Hawaii's eponymous island is more commonly called "The Big Island." It's also the youngest in the chain of volcanically formed islands, and the only one that is still growing. The responsible volcano, Kilauea, most recently started to erupt in 1983 and has been going strong ever since.

The relative youth of the island (800,000 years) means its coast largely lacks the sugary white-sand beaches of older islands like Kauai, though there are a few. Instead, most of its shores reflect their volcanic origins with jagged sea cliffs, black-sand beaches, roughly hewn coves, and sprawling tide pools carved from new lava flows.

The Kona and Kohala coasts compose the central section of the island's western side, directly in the lee of the towering mountains Mauna Kea and Mauna Loa, which block the rains and trade winds blowing in from the east, making these areas dry, warm, and wonderfully sunny year-round.

Not surprisingly, these are the prime tourist centers—home to the Big Island's beach resorts and the best places for Big Island beach action. The calm, clear waters draw crowds of divers and snorkelers looking to explore the submarine lava formations, coral heads, and abundant sea turtle populations, and kayakers can paddle along rugged cliffs en route to hidden beaches and ancient Hawaiian archeological sites.

Whether surfing, boogie boarding, or windsurfing, the Big Island is also a great all-around board-sports destination. With the lowest population density in the islands, localism is rarely a problem on the waves—there are plenty to go around. And the waves themselves are generally well suited to average riders; for monster breaks, head to Maui or Oahu.

The other primary hub of the island is Hilo, on the windward (eastern) side. A world apart from the Kona Coast, Hilo is the wettest city in America, with a refreshingly cool climate. The beaches here don't have the services available on the other side, but the solitude and picturesque settings are unbeatable. Up and down the coast from Hilo, small coves and tide pools spill from the dense tropical rainforest, offering decent snorkeling and swimming, while waterfalls and natural hot springs sit within easy reach.