Load transports with eight or so Navy Seals and tons of infantry. Promote Seals with drill, promote infantry with city defense promotions. Throw in some machine guns too if you feel like it. Bring along a super medic great general to make best use of Navy Seals' march promotion. If you have some infantry upgraded from earlier units with city raider bring them along too. Take coastal cities with the seals and hold them with the infantry, using city raider infantry if you don't have enough seals. You'll have better results with the seals than the tanks when attacking from the sea, though it sounds like you're doing a pretty good job of softening your target with planes anyway. Tanks I just airlift into the cities I've taken until I have all the coastal cities and enough tanks to make a good drive inland. Tanks left in the cities you take are good for attacking units one tile outside the city, since they have two movement points. In my experience following this approach you are unlikely to lose any seals, while you would have to continuously bring in more tanks. Since you have seals with march and drill promotions and a super medic they will take less damage when fighting and be healed and ready to fight again on the next turn, and you can go from city to city along the coast so rapidly that the war will be decided in less than five turns, most likely.