I'm afraid you're probably right about the loss, but only you know where and how the gear was stored and how vulnerable to 10 feet of water that is.
I deeply commiserate with you. We went through a fire in the last six months, with smoke and water damage that made everything on the top floor of the house a write-off. I will never forget watching those wonderful firemen tossing burning furniture from the alley window, to save our house.
Our coverage was not quite adequate, unfortunately, and we decided to have all the written-off possessions returned to us, rather than pay for their replacement out of pocket right away. Some the gear was usable after a cleaning, either by me or by an audio shop. Other gear would have been usable, but poor storage conditions had worsened the damage and we had to throw it away. Some was just burned and/or soaked beyond all hope. Nothing we managed to fix or clean wound up looking ( or smelling ) the way it had before the fire.
At the end of the day, we did have some of our old stuff in working condition, and some new stuff which insurance had paid for. Very few CDs were damaged by water; fire and the cleanup job was what did in the ones we did lose. The entire vinyl collection was downstairs and most escaped the worst--only the reject pile had been directly under a waterfall.
Everything else was totally transformed. I shudder to think of having to deal with peeling waterlogged cardboard sleeves off a collection of vinyl discs. A job like this is very discouraging, as you discover how much work will be required to save what others may consider unsavable. Both attempting the job, or deciding it is too much and letting go of your treasures, take great strength. I wish you all you need.
One thing I do appreciate. After the fire we became "nomads" in our own city for six months. We saw it from another point of view, one that we would never have experienced otherwise. We lived without our possessions, out of suitcases and in temporary accommodations. There is an upside to this, I came to believe, and a potential renewal. It is much too soon for you to tell, and perhaps your losses will be too great, but ultimately you may find it so as well.
May the love of the Lord and the help of our fellows be with all of you.