Maladroxia

Maladroxia (Maladroxia–Coaquaddus) is a unique spot on the island of Sant’Antioco (Sulcis, SW Sardinia) where warm thermal water rises directly from the seabed, just a few meters from the shoreline—so close that, in some areas, you can feel it by pressing your feet into the sand.
Using your material: the phenomenon has been known since Roman times, and the submarine springs in the bay are described as ~30°C “hypothermal” waters, saline and sulfate-rich.

A short walk away, at Portixeddu Accuau (“Le Vasche”), two submerged basins can be spotted near the shore with a mask/snorkel; local accounts often connect them to Roman-era structures used to collect thermal water—though some descriptions also interpret them as evidence of past limestone extraction and transport by sea.