South of the airport is the small island of Senaga-jima which is connected the main island by bridge. A very luxurious hotel with an onsen, Ryujin no Yu 龍神の湯 (translation: dragon-king bath; Ryujin is the dragon god believed to lived under the sea near Okinawa), is situated there. The rooms to stay overnight are very expensive (so I have never stayed there), but luckily the onsen and spa is open to the public. The entrance fee for the onsen is also reasonable. There is even a foot hot spring for free next to the resort hotel, if you just want to relax your feet for a bit.
Like other onsen in Okinawa, you go to the spa desk to check-in and receive your towels and spa clothes. The onsen has indoor baths as well as some very lovely outdoor baths. I didn’t spend a lot of time in the indoor baths or sauna; mostly I cleaned myself at the shower stations and went almost directly to outside. Outside you have some different choices; there are a few individual rotenburo 露天風呂 and then some large baths (1 is a standing bath, so you stand up in it but it is quite comfortable) that overlook the ocean. I enjoyed all of these and the view was really quite nice, it made it all the more relaxing. The water is a bit salty– it is a unique seaside hot spring for sure! If you stay overnight, half of the hotel rooms even have private outdoor baths…!
The spa treatments offered here are quite nice for some pampering. When I went for my birthday, I got a body scrub, a seaweed-mud wrap, some sort of facial, and a massage… it was not cheap, but it was a birthday present from my husband. I felt amazing afterwards… maybe one day I can return.
As far as food, I have only eaten at the Mediterranean-inspired restaurant inside the resort, which was so-so. Some people really like it, and it was okay, but I probably recommend just going over to Umikaji Terrace うみかじテラス (the small shopping/cafe area on the island) and checking out the food there. There are several options from happy pancakes to food you can eat while sitting in hammocks, each of them with just as nice a view as the resort.