LGR himself put up CD images for the game just now.
1.51v CD release
https://archive.org/details/depth-dwellers-cdrom
1.6 floppy release mail order
https://archive.org/details/depth-dwellers-v16
https://www.youtube.com/watch?v=L6S_6VRtzjU
https://www.legendsworld.net/shooter/game/1057