From StrategyWiki, the free strategy guide and walkthrough wiki

[edit] Mission Briefing

Core has been forced to pull back to their primary base. That base contains the last of Core on Hydross.

Priority Critical:
The Core base to the north is all that stands between Arm and secure Hydross... a world from which to stage our forces for the search of the remaining worlds in this system.

Info Feed
The Core base is located in a protected lagoon. The entry will be well defended. Expect stubborn Core resistance.

To complete this mission you must destroy all Core units and Serpents on the map.

END

[edit] Map Info

Planet	Size	Tidal Strength	Solar Strength	Wind Speed	Gravity	Max Units	Water Damage	Surface Metal	Moho Metal
Water World	15x15	33	24	900-3500	112	250	0	3	40