The minelayer is a naval ship used for deploying sea mines.

The Russian minelayer «Marti» and the battleship «October Revolution».
“Marti” was former Czarist imperial yacht “Shtandart” and become the biggest and most effective
Soviet minelayer in Baltic.
Confirmed victories of minelayer Marti achieved with mines:
27 June 1941 (shared with Ural and destroyers Leningrad, Minsk, Karl Marx, Artem and Volodorsky):
sunk German motor torpedo boats S-43 and S-106.
1 October 1941 : sunk German submarine chaser UJ-117 close Hanko.
21 November 1941 : sunk German tug Fohn (303 GRT) on convoy to Tallin.
11 June 1942 : sunk German support-ship MRS-11 Osnabruck close Tallin.
Ship was later recovered but the temporary loss caused distress among the Germans because were lost
84 men and the mine-field was actually known, but captain did not received the proper chart in time.

Ural was the second largest and most notable minelayer in Baltic Fleet, after Marti.
Often sailed together Marti on mission, but her best successes were scored laying fields close Malyj Tjuters and
Bolshoy Tyuters alongside the old destroyer Kalinin in July 1941: one year later these mines sunk German submarine-chasers UJ-1211 on 7/Aug/42 and UJ-1204 on 26/Oct/42.
Again, Ural and Kalinin, in addition to minesweepers T-205 and T-211 laid a field east of Seiskari that damaged the German minesweeping boat R-58 on 9/Sept/41.
Another shared victory (with Marti and destroyers Leningrad, Minsk, Karl Marx, Artem and Volodorsky) was the sinking of German motor torpedo boats S-43 and S-106.

45mm gun 21-K of the Soviet minelayer «Marti». USSR navy WWII photo.

Minelayer «Komintern» of Red navy in combat near Odessa, 1941.
“Komintern” was a former WWI-era “Bogatyr” class protected cruiser and become the biggest Soviet minelayer in Black Sea, differently from “Marti” no victory can be assigned and she was hard damaged by German aircraft in summer 1942, disarmed and scuttled at Tuapse in October as a breakwater.
Okean class survey vessels / minelayers of 201 project