The old dock property can be bought by either Michael or Trevor for $250,000 after the second heist.

For this trophy, this map of nuclear waste can prove to be quite helpful if your filter your map to just showing nuclear waste. There is also a video below showing the locations.

While you play it, an in-game phone app will help you navigate and shows you red dots if you come close to the barrels. The feature shown on the screenshot below that the game will show you the height-difference from your submarine to the barrel, was removed on the PS4 version, though, but it is not too hard at all.
 

Nuclear Waste Locations Video Guide

The submarine is actually pretty durable - if you don't navigate it too harshly, you can get all of the pieces in the same boat.

You may also get a big chopper to lift the submarine out of the water to fly it somewhere else, because the barrels are spread all over the map and the submarine is very slow - but it's sometimes pretty risky, to fly the sub somewhere else undamaged.

Be sure to save your game every now and then (if autosave is disabled) via your in-game phone while collecting these barrels of nuclear waste because it takes some time and keep track of the barrels you've gotten and don't have yet!