There was once quite a debate in the navy about aircraft carriers and if they were relevant. Today because of A.I. able to guide about any kind of vessel at least well enough to make its craft a kamikaze the expectation that modern naval ships will be relevant for winning naval wars may mirror that carrier debate. The oceans may become an evolutionary lab for weapons of war that guide themselves in competition resembling the wild kingdom of sea creatures seeking to eat others while avoiding being ate (or et if you prefer proper anachronistic slang for past participles).
One can become enthusiastic about flying fish with c-4 and saber tooth lasers able to guide themselves or go into a stalking topor below the surface. There will be intelligent nets made of explosives that can rise from the sea to cover and detonate larger craft- really there is no limit to the artificial intelligent and advanced materials that will make the sea a wild and crazy place enabling sudden surprise attacks overnight or even instantly.
People want a very dangerous oceanic ecosystem with very smart attacking creatures so they can have a wonderful arms race and spare no expense that never ends until the final battle for the seas is one my acidification. They may regret the choice to go entirely next gen tech though and long for the days nostalgically when humans sailed aboard vessels of war to launch missiles. Even spies thought the stuff was worth stealing intelligence for at risk to themselves.
Garrison Gibson: books and blog 