With Water Comes Swimming, With Swimming, Diving.

[p0intman]

I was watching this earlier:

Its a tour of Aquarius Reef Base, which is an underwater laboratory. Swimming, and therefore diving has the possibility to shift the entire way we think about large scale combat. I want to be able to dive many kilometers underwater, and below continents with hidden and unmapped passages to fight in and around and use to travel behind enemy lines. These caverns, like their real world counterparts, should really be massive... and dangerous.

So, instead of laying out an entire method of how to implement it, if ever, ill pose this question instead:

What if, under each continent, there were underwater tunnels, caves that were connected to pools and rivers on each side of the map? What if you actually had to guard them and be aware of them?

What if there were an underwater city, like Atlantis.

That would make these waterways valuable. That would force the necessity of a navy for each side. Not just floating tanks and deliverers, but an actual navy.

Suddenly, each continent matters between one another.