The idea of a Shooter-RTS hybrid had been done before, and you might suspect that a game that does both is a game that does neither very well. You'd be right in this case, but Hostile Waters still works so well because of how lean it is. Warfare is asymmetrical, as you never control a large army or build infrastructure and only ever dispatch a handful of elite units from a lone supercarrier, carrying out lightning-fast assaults on enemy facilities and salvaging the wreckage for resources.
The AI, however, maintains large bases and harvests resources with which to churn out massive numbers of units that it'll use to pro-actively hunt down your carrier and units. It's deceptively simple gameplay-wise, but things get complicated quite quickly. You can end up dispatching salvage vehicles, scouting enemy territory from the air for promising targets, and co-ordinating tank assaults to destroy enemy factories, all simultaneously, and all on the way to completing a mission that initially seemed simple. It's fast-paced and seems basic initially, but punishing if you don't keep your momentum up and fight tactically.
And why are you doing this? Well, you're defending the fully automated luxury communist utopia of the "future" (2012) from the resurgent and insidious forces of capitalism. That's not really reading between the lines, either - it's an endearingly goofy and far-out premise, but a sincere and explicitly political one, which was rare back then and possibly even rarer today. It's fairly minimal and a bit daft, but sombre atmosphere, tight writing and excellent voice acting give it genuine weight.
Seriously, if you find anything said about this game even slightly interesting, you should buy it. Few games are this unique, and fewer still were this great.