[Duskguy]

interesting concept which COULD work without breaking the balance of infantry/ land vehicles/ air vehicles.

if we are talking a "continent" of mainly water it could be something like land on the outer parts of the map with a large lake/sea in the middle (which takes up most of the map) in the lake/sea there could be islands, oil refinery type bases/labs. the water covering most of the map could lead to interesting fights between air and sea units while on the far periphery, and along the (hopfully) numerous islands, land vehicles and infantry fight over bases. and being that the outside is land, you wont HAVE to take a boat to get around, it would just be quicker, although potentially more dangerous.

with the boat ideas, i was thinking:
- the leviathan could be used in place of the galaxy for the sea areas, having the player beach the front end of the boat while leaing the rear in the water to be backed out later, and while beached it could act as a spawn point, like a landed galaxy. for the guns, it could act as basically a battleship, although it would have the same amount of gun ports as the galaxy, they could be mortar based artillery, rocket/missile based, machine gun based or flak based guns to fight close land action, anti boat, tank, air as well as artillery strikes against somewhat distant targets (use the MAX mortar thing as a base to work on). would play the role of battleship/mass transport in place of a galaxy in the sea areas.
-then you have the quad like 1-2 person boat which would be intereting to see in waves.
-a light armored boat like the lightning. think of a 1-2 man patrol boat that is something between a lighting tank and a fighter. boat would be fast, lightly armored and have a gun that can elevate for long range engagements, but not air.
-a heavier more armored but slower boat like the predator tanks/ liberator. would be like a destroyer holding 2-3 people, the driver would have a midle, main cannon for ground based combat, a second player could be a right rear turret with 190 degree horizontal turning and then a left rear turret irroring the right. main cannon would be just like the tanks', while the turrets could be equipped with anti ground, infantry or air guns.
- heavily armored 10-12 person amphibious transport truck/boat with 2 guns on top like the sunderer. or perhaps a variant of the sunderer itself with a land/sea drive train, hich would make it slower on land, but able to travel and move slightly faster in water than the reduced speed allows on land.

OR a less radical idea, and one that could be introduced in addition to boats if decided on later.

the boats could be variants of land units. as with the sunderer idea of a land/water drive train. the tanks could be equipped with land/ sea drive trains as well, taking out the need for boats all together. and when this drive train is equipped the vehicles could take on a cosmetic change with a pointed prow or something. with the leviathan idea, you could simply customize the galaxy to have bouys under the base and wings and have it float. it could be a varient that sacrifices armor in return for the ability to float.
and being that these are all varients of the already designed vehicles, the water area of the map could be lessened, perhaps making the map have a bit more land around the sides and more, larger islands in the center lake/sea.

as to the complaint of balancing combat:
-the facilities would all be on land of some sort like platforms or islands or on the surrounding land around the lake/sea.
-you would have ground vehicles on the sides, perhaps a few spawned or somehow transported on the larger islands,
-infantry combat on the island/platforms (tanks cant go all the way in facilities, and neither can a boat). infantry combat would mainly be in confined spaces and besides boats, be the biiggest component being that bases can only be taken by infantry.
-air units would mainly be fighters and bombers although galaxies could perform air drops over the water since they cant land on the smaller islands/platforms, but maybe a good pilot can get them on the larger islands. and so air combat would be the second/third major vehicle besides boats.
-and finally sea vehicle combat which would be a main component with land combat (only infantry can get in and take bases)

edit: seems i had many the same ideas as kipper, which being that i only read the first two pages before posting is coincidental. but then they say great minds think alike...and the simplest solution is usually the correct one.