Saunarium M15 is a seasonal sauna complex on Sopot beach beside the M15 restaurant, about 800 m from the pier towards Gdynia (beach entrance no. 15), with windows facing the sea and the pier. It runs from October to March. Sauna masters lead sessions every day from 6 to 9 PM and on weekend mornings from 7:30 to 11:15, and guests cool off and winter-swim in the Baltic.