Hin Ta Hin Yai are the most famous and most visited rocks in Koh Samui. Reminding the shape of the male and female genitals, Grandpa and Grandma rocks are located at the end of Lamai Beach. A legend writent on a board there tells the story of an old couple, Ta Kreng (grandfather Kreng) and Yai Riem (grandmother Riem), who lived with its son in the province of Nakhon Si Thammarat. When their son arrived at the age when it was time to marry, they decided to go by boat to the neighboring province of Prachuap Khiri Khan to ask for the hand of Ta Monglai's daughter. During their trip, their boat was caught in a storm and they were thrown into the sea. The old man and his wife died drowning and turned into rocks, Hin Ta, Grandfather's rock and Hin Yai, Grandmother's rock.
It is one of the very touristy places in Koh Samui, there are almost always a lot of people except early morning. But besides the shapes of the rocks, the setting is really beautiful so if you can, make it at least a quick stop here.
Just above Hin Ta Hin Yai, there is the Lamai Viewpoint that many people miss and it is a pity. The view is more dominant and you can see on both sides with on the left an unobstructed view over Lamai beach and on the right Hin Ta Hin Yai and Hua Thanon beach. THe viewpoint can be reached by a small staircase behind the toilets.