Ships are unimportant.
Even on a 80% Archipelago map.
They are no "wooden walls" that protect your main island from invasion.
You just need transports and a destroyer or other warship escort for them to ship around your troops before Airports.
England and the C3C Manowar are effective in disrupting enemy shipping, because you can enslave a large fleet of fairly effective Manowars.
But in general, land and air power are clearly supreme to naval superiority. Even if your enemy totally owns the seas, you can usually slip through with your transports and build an Airport in modern times.
Also, ships are easy prey for aerial bombardement. Since lethal sea bombardement even more. There may be some truth about that, but the AI does not use carrier groups proper, and they cannot stand a serious bomber attack.