Underwater boat storage

After seeing pictures of boats piled up after recent hurricanes I had a "crazy" idea about how to protect them: sink them. This idea is definitely halfbaked and could use some input from subject matter experts. And it could be completely dumb as well.

After a little research, I see that the preferred method for protecting a boat from a hurricane is to pull it out of the water if possible. That may be very difficult and expensive with larger vessels, and even then, unless they can be hauled out of the path of the storm, there is potential for damage. I did find one reference to people sinking houseboats before a hurricane to reduce the chance of major damage at the cause of guaranteeing some damage, so this idea is not completely original. But houseboats I'm guessing would still be mostly above the water when sunk, and would be damaged similarly to a partially flooded home because flood water would flow through the cracks in the door, etc.

For a regular (or maybe only slightly modified) boat, it seems like it might be possible to sink it with very little damage.

Sinking them in the marina probably isn't a good idea because the water is shallow enough that other debris could easily end up on top of the sunken boats. It seems like you'd want a place not too far offshore (for ease of access) that has fairly deep water to reduce the currents from the waves and storm surge. A sandy bottom is also a good idea.

Doing this for a single boat would undoubtedly be quite expensive, but if a system was set up to sink many boats in an assembly line fashion, it might not be too bad. I image a line of boats headed out to the storage location. Small boats would come up boats approaching the end of the line and make sure that each was prepped and ready to go, then the filling from a tanker or a pipe from shore would commence. A sub and/or team of divers would guide each boat to the bottom and "park" it safely.

Technical details:

Obviously the first thing is to fill it with clean water, which is much better then dirty salt water.

We probably want to add something to the water to prevent algae and/or mold growth as it is being dried out. I considered filling with propylene glycol, but that might be hard to dry out, and expensive. I'm assuming that all the hatches can be closed and are basically water tight so that salt water doesn't mix in with the fresh water.

The engine would take special consideration. We don't want to get water in the engine and we don't want engine oil contaminating the water in the cabin. Small amounts of contamination from the engine to the outside of the boat may be tolerable if fewer boats cause bigger oil spills from being destroyed. It might work to completely fill the engine with oil. Ventilated components like starters and alternators might be an issue. Maybe the best solution would be to have a diving bell over the top of the engine and have a compressed air tank that automatically adds more air as the boat submerges.

A boat specifically designed to be able to do this might have a built diving bell and have easy to use ports for filling and emptying water/air in the cabin.

I understand that some boats have positive buoyancy due to foam, etc. Hopefully enough ballast could be safely added. Of course we'd probably want some ballast in all the boats to make sure they don't slide around the ocean floor due to currents.