The Naval Museum of Simi is located in Gialos, just 2 km from the main town. The museum was established in 1983 and in 1990 it found its home inside an elegant neoclassical house, where the central shipyards of Simi were housed in the past.

The Nautical Museum of Simi displays old maps, ship models, diver suits, nautical tools and other exhibits that depict the long marine and sponge-fishing tradition of the island. In fact, there is a special section dedicated to sponge diving with exhibits including diving suits, diving machines for oxygen production, a collection of sponges, diving stones and others. The museum also hosts paintings and wooden-carved sailboats of the craftsman Antonis Polias.