Another way to think about it is specific weight. Ships have fewer kilograms per cubic meter than water does so they float. When pierced they start filling up with water which makes their specific weight go up and eventually become more kilo per cubic meter than water. At that point the ship sinks.
But why so complicated? A 10cm metal hull seems much safer than a 5mm opening with hydrophobic coating.
Also with a chamber system ship's can be made pretty robust and almost unsinkable.
In practice this is something that's actually done quite a bit. Fill a lot of air spaces in a boat with foam and you get to the point where if your boat fills with water you can simply pull the plug in de bottom of the boat and it will un-sink itself most of the way. You see this for example on small sailboats, the only caveat being you can't be on the boat as it's un-sinking since you'd weigh it down.
That said, seems to me that foam is a lot cheaper and easier than micro-engineering every surface on the boat.