Yakushima is famed for its forests and mountains, but of course, as an island there is also the sea to pre-occupy you – particularly during the summer months. Sea activities include snorkelling and diving, sea kayaking, sunset-watching, fishing and turtle-watching. You can even take a hot spring next to the sea – the Hirauchi Kaichu Onsen is a natural hot thermal under the sea and the bath is accessible at low tide!
The rocky coastline of Yakushima is undeveloped and you'll find that even in the high season beaches are peaceful and uncrowded. Half of Yakushima's beaches are visible from the roadside, but half of them require some local knowledge (these are usually the better ones!). A word of warning though, please be careful when swimming as the coastline around Yakushima often becomes deep wery quickly there can be a very strong undertow (especialy in the south of the island). We advise you to stay close to the shore or only swim at the designated swimming beaches. The safest beach is perhaps the Isso Beach.
You can swim and snorkel comfortably from June to October, while the diving season is all year round. Due to the warm Kuroshio current that flows past the island then even in the winter the sea temperature around Yakushima rarely falls below 20C.
Between May to August you can take a YES tour to watch the sea turtles come ashore at night to nest. These turtles are now protected and there are certain rules that you must follow whilst on the beaches.