Prior to discovering SPWaW with its extensive Pacific Theater gameplay (and thereby taking me away from any other game as well as ship modeling), I spent alot of time with Fighting Steel.
As with SPWaW, FS (by SSI) was allowed to be "adopted" by an organization for the purpose of updating, expansion, etc. FS is a free download and there are a large number of add-ons and scenarios available for the sim. It is alot of fun. Information on FS and other purely naval sims can be found at the NWS site at:
http://www.navalwarfare.org/
While not naval combat only games, I would also recommend the old Great Naval Battle series (Volume I-IV), especially Volume II, Guadalcanal. It is an old DOS game that has ship-to-ship battles as well as a limited ground combat aspect. In GNB II, players basically have to get their troops/supplies/aircraft loaded, moved, and landed at Guadalcanal. The ground combat is simplistic but from a naval aspect, there is lots to do with your various TFs and individual ships as well. There are both carrier and surface ship battles.
About the same age is Task Force 1942. Again, this is an old DOS game that I spent alot of time with. In TF 1942, you focus mainly of naval engagements around Guadalcanal and the Slot. You can also operate and fight individual TG, TF, and individual ships. Both games have campaigns.
While dated, both games represent an important point in WWII naval sims IMO.
Other old naval games: the Carriers at War series by SSG (also revised/updated) and of course, Carrier Strike by SSI and Pacific War: The Matrix Version (nee SSI).
If you are interested in modern era naval sims, the Harpoon series and the old Jane's Fleet Command (also reworked by NWS) are examples. I can't attest to any details because I haven't played them.
Even older is Aegis: Guardian of the Fleet, an old DOS game.
For subs, you have a bunch: Wolf Pack, Silent Hunter, Silent Hunter II, Aces of the Deep, Seawolf, 688(I) Hunter/Killer; its sequel, SubCommand. Lots of fun and a good size community of serious fans/players, add-ons, etc.
Hope this helps.
Ray