This strange derelict industrial site 300m off the coast near Babie Doły, north of Gdynia, was built by the Germans to research, build and test torpedos during WWII. Connected to the shore by a pier, the Germans abandoned it in April 1945 and it fell into disrepair. To stop people from accessing the building, the pier was blown-up in 1979. We certainly don't recommend swimming out to the site. However, there are boat companies like riby.pl who can take you out there to have a look around - the cruise lasts 1 hour and costs 900zł; a minimum 9 people are required.