Russian frigate Admiral Makarov
The Drive reports, it appears Ukraine made a mass attack of unmanned air and surface craft on Russia’s primary naval base in the Black Sea, Sevastopol (Ukraine is not claiming responsibility). There seems to be confirmation from Russia that minor damage was done to a minesweeper, but other reports indicate a relatively new frigate, the Admiral Markarov, serving as flagship of the Black Sea Fleet, may also have been damaged. Video in the report shows a very close approach to a frigate of the same class, apparently by an unmanned surface craft before the video ends abruptly.
Russia is also claiming that the UK was involved in the planning of the attack.
While unlikely, how to defend against such attacks probably should be in the Coast Guard’s skill set. Force protection and harbor defense are potential missions.