Naval bombers, Subs can't see other subs, Destroyers will get easily bombed by battleships or cruisers, naval bombers tells you when something passed there, including subs, and can also deal damage to landing forces.

Naval bombers with some stacks around of capital ships like cruisers and or battleships protected by destroyers.

And if i Need a marine line in the Sea?Not near my coasts,top much aircraft carriers Is so expensive
then submarines

Yeah, in that case subs, but I’ve never had a case of needing a naval line in the middle of the sea. Just send a few stacks out into the sea to patrol and hunt down enemy stacks. If they reach your coast, your naval bombers will take care of them.