Visited yesterday, obviously without charging since I don't have a boat (yet?).
I had to play some geoguessing to find where the charger actually is because the "address" is not mentioned in the online articles about it. But I identified it's in the "Hafen Lachen" and now I have geotagged pictures to confirm it.
Despite most boats being in storage, the charger seems operational. On the charger screen it looks just like other Kempowers connected to the Swisscharge network. Unfortunately I couldn't make out the plug numbers from the distance and I didn't have any way to zoom optically. If anyone knows the plug IDs, it would be interesting to see the pricing on the Swisscharge ad-hoc payment page.
GOFAST put their #swissmade stickers on the charging cabinet which feels a bit out of place since that particular maker of charger is not Swiss. I guess it's referring to the fact it's operated by a Swiss company.