Something else I noticed that you all probably already know, you can't give a prerequisite for a unit that is a resource in the water, the unit will never be built.
I tried using a water resource (Octopus) as a prerequisite for building a unit, cities with octopus never had the option to build that unit, I am guessing that there has to be a road to the resource, therefore; can't be done.
Can someone confirm to me that only resources on land can be used as prerequisites for units.
For a random map game, this is true - you cannot build a road to a water tile, so it is pointless to use water-based resources as a prerequisite for something.
However, there is a workaround for preset map scenarios. The trick is to allow Colonies on coasts, and put your resource, say Octopus, on a coastal tile right next to land. Then, while still in the editor, place the colony assigned to whomever it is supposed to belong to. Then, when you give that civilization a city right by that coastal tile, when you load up the scenario in Civ3, the city's cultural borders will destroy the colony, and the colony will be replaced by a road on water.
You won't be able to upgrade (or pillage) the road, although it may be able to be bombed. If someone conquers the city and the resource is now within their cultural borders, they should have access to the resource as well.
I don't see how this would work for resources farther out at sea unless you had multiple contiguous colonies stretching out to the farthest resource. So it would only work really well for resources at sea close to a civilization's cities. But it would work just fine for that.
The attached .sav demonstrates this. In this "scenario" (test of concept really) I generated a map, allowed Oil with no technology prerequisite and allowed both Oil and Colonies on coasts, put Player 1's start location by the coast, and put an Oil Colony belonging to player 1 right by where they'd build their first city. Load it up into Conquests 1.20 - 1.22, build the city, and you'll have your oil connected to Trondheim from its water-based source.
Never seen that strategic resource popup before, by the way. Nice find - I've been playing this game for more than 5 years and still haven't found everything!