Deadly Seas
 

http://www.latibulum.com/pvk/Dom3/DeadlySeasMod.jpg

This mod effectively removes most of the undersea conquest from the
game. Some elements remain - mostly provinces which have amphibious
populations. This means that nations with some amphibious units
(such as Agartha, or Late Ages Mictlan) can still make (limited) use
of them. However the fully undersea nations are removed, and aquatic
independents now have extremely powerful water elementals (including
random underwater independent attacks), which means that most seas
are effectively off-limits.

The specific changes are:
* Underwater nations are removed.
* All aquatic independents are replaced with extremely powerful
immobile units which are almost insuperable.
* Now-unused Coral Queen renamed to match the Sea Guardians, so
the Wish spell can't be used to summon the superpowered ones.

The purpose is to offer a game where undersea conquest is only a
minor part of the game. This is for those players who may not want
to include undersea conquest as a major element in all their games.