Coastal tiles make sense to take over especially if you have submarines which can benefit from them.

[s0nny80y]

I think with the submarines bonus to attacking into coastal tiles, it makes sense to take over coastal tiles near your city.

 

[vorlon_mi]

Yes, I usually always take that attribute. Both for defense -- firing on an attacking melee ship next to my city -- and for offense, when attacking an AI city. It's rare that I'm using my subs out in the open ocean, in ship-to-ship battles. If I'm engaging an AI ship (or group of ships), my carrier-based planes hit them first, followed by my destroyers/attack ships. The subs are way too slow: either 3 or 4 movement, while the attack ships have 5 or 6 movement.