Krabi has some great areas for snorkeling and diving, and if you're inexperienced, there are schools for both. You can snorkel right off one of the beaches, but you won't see that many fish. The best way to snorkel or dive is to either join a tour or charter a boat (the local boats are called longtails) and have the boat person take you to a nearby island.
Boats and tours are available from Ao Nang or Railay beaches. The snorkeling tours usually provide lunch, a snorkel and mask, and a life jacket. If you don't have your own diving equipment, you can rent. The waters are crystal clear with colorful coral-covered plateaus and walls, and fish, such as grouper, black-tip reef shark or large schools of snapper. While diving, you can see these plus whale sharks, manta rays, shrimp, crabs, barracuda and leopard sharks.
Exploring the beaches and islands in Krabi is easy with a canoe or kayak, which you can rent at Ao Nang or Railay beaches or Krabi Town. You can pack a lunch, bring your snorkeling equipment and explore on your own, or join one of the tours that takes you along the coast or around the area's islands.
Sailboat charters are also available with destinations such as Phang Nga Bay at the north end of the Krabi coast with over 100 islands; the islands of Koh Rok Nai and Koh Rok Nok with their abundant wildlife, dense vegetation and steep cliffs; and the island Koh Lipe to the south, one of the few islands offering accommodations and restaurants.
Railay, a popular beach in the Krabi province has rock climbing and trails that lead into the jungle. With over 700 climbing routes, rock climbers from beginner to expert will have a worthwhile climb. Climbing schools are also available in Railay. Only experienced climbers should attempt some of the climbs. For instance, one area has three rock faces to traverse with only ropes to support your weight. But most of the rocks have natural footholds because of the nature of the craggy limestone. Be sure to wear a good pair of shoes if you plan to climb.
For hiking, there are relatively easy hiking trails that take you to beautiful views of the water, surrounding beaches and islands. Some of the more difficult trails lead to tranquil mountain lagoons.