The upcoming update is scheduled to arrive on April 27th. It will bring a set of naval-related features including naval bases, submarines, and naval skirmish maps. It will also introduce two new weapons, AI difficulty customization, as well as many other less major improvements.
Submarines
Submarines can be built with the help of a new propulsion module called Ballast Tank. Equipped with enough of these modules, a unit can freely submerge and surface at any time when in water.
When submerged, submarines are less vulnerable to some types of damage (kinetic weapons do less damage, lasers and EMPs have no effect at all). These units can be very advantageous on maps with large bodies of water.
Naval Factories
Naval Factories are factories that can be built on build pads which are placed in water. They act the same as field factories with the exception that they can be used to deploy units that cannot move on land. More information on naval base-building will be posted when the update arrives.
EMP Gun and Large Railgun
The upcoming update will add two new weapons - EMP Gun and Large Railgun. The new railgun, like the artillery gun, inflicts a lot of damage per single hit, it is relatively slow to aim, and has a significant cost. Unlike the artillery gun, the new weapon shoots very fast projectiles that can reach their targets almost instantly.
The EMP gun, instead of inflicting damage, drains the energy of its target by a set amount per hit. Its projectiles also immobilize the target unit for a few seconds. EMP guns are very useful against fliers, which can be trapped and destroyed with a few well placed shots.
More information on all the new features and additions will be posted when the update arrives!