It's not even really a fireship. Those were more like the demolition destroyer in Operation Chariot. The Ukrainian robots are just unmanned forms of kamikaze motorboats like the Japanese emergency anti-landing craft boats, which is the proper analogy. For a more modern example, the suicide attacks on USS Cole can be considered, as well as the Italian commandos, who pioneered the concept in combat use.
en.wikipedia.org
This is just what happens when you are defeated in the naval realm, and cannot meaningfully contest sea control by the enemy, but still have a coastline under your control. Russia can't control Odessa so the Ukrainians send stuff like this. Honestly, sending MiGs or Su-24s armed with laser guided missiles or EO rockets like Kh-25, which Ukraine has plenty of, would be actually lethal to warships in general, but they don't have enough of an air force to do that either.
The comparisons in the aero-naval sphere to Japanese Empire are pretty stark, if only because both nations were under then-impenetrable naval blockade, at least.
So far no naval blockade has ever been broken by tiny explosive laden motorboats or kayaks but plenty of naval port strikes and minor annoyances have been done. If Ukraine had a few more batteries or battalions of functional Neptunes it might help, but they don't seem to be able to pull off the Moskva strike again, as perhaps the Krivak Vs have better ECM or better littoral air defense than the 1960s cruiser, or maybe they don't have enough anti-ship missiles, or Russia is keeping its Krivaks further away. It's not really clear what's going on besides Ukraine isn't going to be able to break the blockade any time soon, at least not without invading Crimea, if that.
I'd say this is where a diesel sub is useful but Russia has oodles of them in the Black Sea Fleet so it wouldn't change the calculus much. Ukraine would need a functional air force that's able to take losses, which it doesn't have, and maritime patrol aircraft for anti-ship/anti-submarine strikes, which it also doesn't have.
Thus, the little robot kamikazes are the only materially effective option left, even if it seems to be rather minuscule.
It's hardly a new naval tactic, but it's one done by a naval force that is greatly inferior to its enemy, and can be surprising at times. Perhaps they might pull off one, maybe two, more similar attack before the harbor defenses adapt. I suspect Russia would start flying Helixes or Hormones with surface search radars, not unlike how the USCG flies radar aircraft to detect narcosubs, near the harbor mouth tbh. A lightweight anti-tank missile like an Ataka would be the ideal weapon to use, which Helix and Hormone can carry, and is directed by television or FLIR sight.
www.navyrecognition.com
