This is a messy area of state law in the US but the basic gist everywhere is that you can't own land that is always submerged. You might have significant ownership rights to land that is sometimes submerged but the state has significant rights to that land as well. You have rights to do things like build docks connected to your land but these are subject to various limitations. If you start getting into stuff like mineral rights or the right to dredge you are in complicated law and need to get an attorney who does this kind of stuff. People with lots of money abandon these things when they find out what a mess it is.

Edit - I also know absolutely nothing about Florida law and wrote the answer somehow ignoring you told us you were in Florida.

I'm pretty sure an asteroid will hurt earth also. It may be 7500 years, but it may be next year, I'm pretty sure it will happen.

I live in Pinellas County, Florida (across the bay from Tampa) and being a believer in science, I think my property will be under water from global warming in about 75 - 100 years. Being on a high point in the county, I’m pretty sure I will probably see many houses and properties be submerged in my lifetime.

My question is this – Will the property still belong to me (or my children) when it’s completely under 3” of seawater?

If so, I’m going to start my floating water bottle island anchored to my backyard now.