This is a Ukrainian sea-drone. That have been very effective against Putin's decimated Black Sea fleet. Turns out the Black Sea commander was an ultra vodka swiller, so has been fired. Iran was quick to pick up on sea drones. The IRGC has used them too, from their base in Houthi Land. So far blowing up one cargo ship.
Little bitty water craft. A WW2 destroyer and it’s 40mm bofors mounts would chew them them up easily.