This is a small thermal bath not far from Kos, easily accessible by bike or baggi. When arriving during low season, don't listen to a lady from the bar on the top of the hill. You can easily ride down by baggi or car and park on a small parking down-below.
The thermal bath itself is a small area in the sea separated by stones. So you can relax in hot thermal water and then swim in the sea.
I guess there are crowds in summer but in October it's quite.
If you own or manage Therma Beach, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.