From: Corpus Christi, Texas
I haven't thought this completely through, but what about a system of coastal hexes, areas(island chains) with hexes and for the open ocean an area without hexes.
The idea being that it cost different movement points to traverse from one area to another and also dependent on the assets in each area a level of detection dictates whether combat takes place or not.
OK so like for coastal hexes, the ones adjacent to land areas, it cost 1 MP, unless of course mines or some other obstruction exists then the cost goes up. These would also be the hexes of greatest intel so combat(intercepts) are highly likely.
If a fleet moves from a coastal hex into a more open ocean area, the areas with hexes, then it will cost an additional amount of MPs, say like 10. These areas with hexes would be configured with the island chains on the borders of each area so that island chains could control the intel of the area dependent upon the assets deployed. This also means that there could be conflicting islands chains on the border of a single area, say opposite each other, like the Marshalls and Gilberts.
Now if a fleet or naval unit transits to an open sea area(without hexes) which simulates the vast areas of ocean then it would cost additional MPs, like 20 as an example and it would occupy an hierarchy of status(as in WiF) for future operations.
Obviously this can get a little complicated for fuel usage and various interactions of intercepting air and naval fleets, not to mention subs but it could be worked out with a good programmer and the right coding language.
All this is loosely based upon a game by SPI I used to play called "Pacific Theater of Operations". Don't remember it really well, don't know where it is, but perhaps some of you can recall some of the aspects that could be pertinent to this conversation.