The main reason to go to Pulau Weh is for the beaches : relaxing, swimming, snorkeling and diving. Go straight to Iboih or Gapang beaches. Single dive starts at US$27, cheaper the more you do and there are 20 dive sites which are way less populated than else where in Indonesia. Please note that Iboih Beach are closed to diving on Friday mornings.
The house reef at Gapang beach boasts a wide range of macro life including rare critters like Frog Fish, Star Gazers and Gurnards. Large pelagics like Mantas. Whale Sharks and Mola Mola also come to feed when the season is right. Gapang Beach also have a sandy mangrove beach. When it is high tide, the water gets very clear and during low tide you can discover hidden sea lifes such as baby octopus, baby lobsters on the shallow water.