Thanks Yuri352, that's what I suspected. The GWAS & SWAS system uses a combination of campaign and 'battle' paper maps. In a campaign game when two fleets move into the same rectangle (they are arranged alternately almost the same way as hexes) and spotted they transfer into the plain battle/tactical hex map. If ships are about to go off one side of the tactical map then everybody is slid to the opposite side by one or more hexes. While you would need more space than an ASL scenario, a reasonably sized table should do. The series games include both tactical and campaign scenarios, only the campaigns need the campaign maps like the Mediterranean or North Sea.
As I said, while the damage model seems good (but I am no ship expert), the speed, armour and gunnery factors are a bit fudged, but work. Neither system is as detailed as ASL in that respect, more akin to MMP's PanzerBlitz 2, but still, I believe, a great improvement over the early AH or SPI efforts. If you want to try both systems at once then AP's "Cone Of Fire" is your best choice as it has both rules variations and has ships for combat around the lower part of S. America, someone might have a stock of that. Between the two systems they cover everything from Spanish-American War to WW2.