Should R'lyeh and Atlantis swim upriver?

[Targa]

For those who haven't been following the map thread:

I'm in the process of making a new map, which has a sea and several lakes. The lakes are all connected to the sea via rivers (all but 1, which will be connected in the wrap-around Version of the map). You can see a preview of the (unfinished) map here:
http://www.techno-mage.com/~targa/webmap.jpg

I am still new to the game, and have yet to play as R'lyeh or Atlantis, so I really don't have a feel for what's going to play best, or be in the best interest of game balance.

The question is:

Should the inhabitants of R'lyeh, Atlantis, or any other nation that acquires aquatic/amphibious abilities be able to "swim upriver" to the inland lakes (or vice versa)? ie: The lake provinces will be #neighbor to the adjoining sea provinces. You can see a quick reference to what I mean here:
http://www.techno-mage.com/~targa/webmap2.jpg

Some have suggested that the two water nations are already powerful nations in their own right, and that allowing them to gain "instant access" to interior landmasses would put other players at a disadvantage. What's your opinion? Take the poll.