[struwwelpeter]

Russian navy in the late 19th century experimented with round ships called "popovki". The Vice-Admiral Popov and the Novgorod were constructed as heavy-gun, shallow-draft (cue Lt Chekov) "wessles" for guarding coastal cities and river mouths.

Supposedly they were scrapped in 1912, so I can't imagine one of them ending up on the bottom of the Baltic.

[Tijeras_Slim]

Wow! The Russians made crazy stuff before the Commies!

[Calvin Locke]

Russian navy in the late 19th century experimented with round ships...

Last I heard, the Chesapeake Bay still uses seasonal round "lighthouses/barges".

After ice season, they are towed to locations, and literally screwed in to the mud via a central auger.