Styrene used to float downed ships.

Factual Questions
1

I ran across information where a submarine or ship was raised with styrene pellets. The styrene was heated to expand into it’s air holding sized pellets on the salvage ship, and shot down a pipe into the ship. Each pellet held air and so unlike filling a ship with air the pellets held the air in the ship. Where as air pumped in would leak out, the individual pellets hold the air.

I can’t find the information again, can anybody else? I thought this might be a solution to raising the Russian sub or the fishing boat the Navy just sunk.

2

While polystyrene is used, I believe that urethane foam is the more frequently used material. It is fairly standard practice to use it in salvage efforts, now, just the way you described it.

(I do not remember whether or not there are issues related to depth. I have a vague memory that below a certain depth, the water pressure is sufficient to keep the foam from expanding so the foam does not displace the water with more volume and less weight, resulting in a decided lack of buoyancy. I do not have any particulars on this.)