The AD&D DMG is just terrible in its treatment of ships. It's a seemingly random collection of tables strung together with not much of anything except a common header, an emphasis on the minutae of how long it takes a large barge to reach normal speed from a standstill, and no real treatment of what the players themselves will be doing on a ship in the first place.
2nd Edition's "Of Ships and the Sea", and 3.x's "Stormwrack" go even further. There's plenty of delving into the differences between tropical, sub-tropical, arctic, etc. encounters, and new classes, feats, kits, etc. to allow players to specialize in all things nautical, but I wonder if any of that actually got used outside of a specifically sea-based campaign (if then). I'm not interested in the undersea sections of either book, because I think the current section in the Adventures Dark and Deep GMT does a pretty good job without getting into minutiae.
The D&D Expert Set takes us in the opposite direction. It takes up only two printed pages at the end of the Expert rulebook, but in those pages we manage to learn about siege weapons on board ship, a straight-percentage table on evading encounters, wind (*plus* an optional system of "simple rules" which is longer than the table it replaces), and stats on 11 types of ships.
I've been pouring through all of these sources and more, and getting more and more frustrated. The same way I was frustrated with pouring through the sources on castles and armies, and then realizing that nobody was using those rules anyway, so why kill myself over them? Characters are on ships a lot more than they build castles, so I should turn my attention there.
And it struck me tonight that I was doing the same thing with ships. Nobody is using AD&D to simulate detailed combat between ships, or cares what the wind is like every 6 hours of a 4 month journey. Characters on ships do three (non-mutually exclusive) things:
1) They use ships to move from place to place
2) They use ships as encounter locales just like buildings or dungeons
3) The ships they are on get into hostile situations
Now that this conceptual design hurdle has been overcome, look to see the next version of the GMT available for download soon. Many thanks to Mortellan over at Greyhawkery for getting me thinking on this subject in a comprehensive manner.