realism wise - yea shells that do damage underwater may exist, but I doubt that them being fired on surface of water above a submarine's maximum depth and horizontally would do anything to that submarine x meters below, instead of being fired at it from directly above or however they are supposed to, or that battleships would use those specific shells as their standard ammunition vs non-submarine targets as well (because battleships dont change what they fire when groundfiring submarines) considering that isnt even what they are designed for, or that they would even do aoe damage
also saying "future technology has shells that can shoot submarines underwater because future" and "atlantis cant stay underwater because present" at same time?
I would like to see submarines taking longer than a second to surface/go underwater if thats what it takes for them to not get hit by surface weapons