Drones are just another form of ammunition in this case. Dropping something like a torpedo from the air against some ship makes sense, as damaging a ship underwater is obviously a good idea. That is hard to do if you attack from above. Launching flying drones from a drone boat also is sensible, as it allows you to attack land targets. In the case of Ukraine it also allows different directions of attack. Land to water is really not a good idea, as you need to drive to the coast and then also need deep enough water to actually have the water-based drone be able to swim.