Naval Artillery can be your best friend and your worst nightmare, in one call!. If you took artillery, made it have the radius of a bomb, and fired up to 20 shells of it, you'd match what naval artillery does.
To use such a doomsday weapon requires a signaler and any number of TPs. It fires one round of the bomb–sized artillery per Tactical Point you have. The explosion will be preceded by a growing black circle, so you know where to move your men from. Note that the Tactical Points points are deducted at the end of the signaler's call, so if you have 12 TP, call for Naval Artillery, and then 3 more waves arrive before your signaler completes the call, all 15 TP will go to the Naval Artillery strike, not just the 12 you had at the beginning.
Be Careful! Naval Artillery is incredibly inaccurate, and if your men are not under cover, it will blast them, along with the enemy, to pieces. If you have 10+ TP's and then use this, you might as well go inside a pillbox, because the enemy is going to be shredded.
Overall, Naval Artillery is the most powerful, but also the most dangerous support option at costs of 4 TP +. If you have only 1 TP it can be a better deal than the bomb drop because of the much lower cost. However, it could also blast your squad to pieces. Overall, it is a good last stand weapon if you get surrounded by enemies. But if you are not in a last stand situation and have enough tactical points for a bomb or arty strike, it might be a better option to go with one of those two.