Once years ago most of the sento along the Osaka Bay would build pipes to the ocean and suck that salt water up, heat it up and make a nice bath out of it. Sadly, all those baths are gone now except for this one, Minatoshio-yu in Sakai. A 2.5km pipe runs from the bathhouse to the harbor where the water is pumped back. It is then stored (and assumedly filtered somehow) before being put into a boiler and then an indoor bath an outdoor bath. Otherwise this is an above average sento with a good electric and deep bath. The cold bath is a bit small and could barely fit two people. That said it is a great sento with a unique history that it worth experiencing.

Old Review
According to their webpage this the last surviving salt water sento in Kansai. The salt isn't as strong as straight ocean water so it doesn't leave you sticky, but if you have any sore spots they will sting just as my inner thighs did. Ignoring the stinging the salt water is very refreshing. They pull the water from 2km away, run it through some processing, heat it and pump it into the baths. If you happen to get any of the bathwater in your mouth, you'll know for sure that it's from the ocean. Minatoshi-yu looks recently remodeled and has a very clean feeling to it. It's very bright and open inside, despite its low ceiling. This is in contrast to the cluttered lobby that seems to be the gossiping spot for the local grandmothers. At least the night I went there was lots of chatting going on. I also think I heard the grandmother behind the counter ask her counterpart at the food bar, "Gaijin daijyobu desuka?" (Are foreigners ok?) when I entered. I didn't hear the reply, but I wasn't asked anything unusual at the counter. Perhaps foreigners are a rarity there, or the grandma was filling in for the typical front person Just didn’t know what to do. I know of two Supersento in western Kobe that also have saltwater baths, but haven't yet added them to this page. The salt water is an uncommon in sentos and worth trying at least once. I would put this down as one of the more unique sentos in the Kansai area and worth going out of your way to try.