If you have enjoyed Jeju by the beachside, you are nothing but a boring tourist!
There are much more to Jeju ocean than just white sand beach like Yongcheon, port, wetland bay naturally created with basanites, or small naturally formed pools where you can enjoy water sports.
Seonnyeotang or "Taoist Fairies' Bath" by Hwangwooji Coast. Like Queen's Bath in Hawaii, this is a natural formation made by the constant ocean waves. Depending on the depth, there are three sections.
The reason why this Seonnyeotang is greatly beloved by the people is that the breathtaking view. From Oedolgae Rock, walk along the trail along the coastal line which leads to steep staircase that ultimately shows you the panoramic view of Seonnyeotang and its surrounding. Right after the rain, you will find a small waterfall naturally form by this staircase, so if you are lucky, you get to enjoy the bassanite cliffs, columnar jointing and the beautiful view around this staircase.
Seonnyeotang is made up of the main pool with 5 to 7 m (16 to 22 ft) depth and two small ones under 1 m (3 ft). And the best time to enjoy these pools is when ebb tides are turning to flood tides. At low tides, it is difficult to swim in the two small ones and you would also have to slide down on a rock to get to the main pool so it is highly recommended that you visit an hour or two before the flood tides. As any Jeju ocean is, Seonnyeotang is known for its clear and clean emerald-hued water.
Bring yourself the right gears like GoPro or snorkeling equipments and you may easily take shots like that. Just remember to be there when not many people are around!
You can also rent snorkeling equipments and life jackets; so don't worry if you didn't pack them with you! And when the water can rise rapidly and swimming can be limited or entering may temporarily be prohibited. So beware and always play safe!