On a pure water map, ships are very strong compared to hover and amph, ill focus on apmh vs ships
Ducks get kited indefinetly by hunters, meaning taking a upfront fight is never good.
Ducks are mostly for flanks and dealing with and acting as subs against other ships that cant fire underwater
You probably need archer to deal with hunters, since they are tanky enough to deal with hunters and have AOE
Scallop only really has use if its lobbed, its underwater dps is worse than ducks
Buoys are ok, but need to float and unfloat often to avoid taking return fire from mistral, envoy and the impaler missile from siren
Buoys with archer duck is probably the best option, but you need enough buoys to deal with siren
Grizz functions as a heavier buoy essentially, bulkhead might have some use, but i havent used them too much recently
On a pure water map where you cant take advantage of going on land, ships is usually a better plop than anything else