Acoustic beacons exist for underwater position [0]. They usually connect to a transponder on the surface. Not sure this thing had one. Reading this: "This experimental vessel has not been approved or certified by any regulatory body, and could result in physical injury, emotional trauma, or death."[1] makes me think it was a disaster waiting to happen.
[0] https://iopscience.iop.org/article/10.1088/1757-899X/612/4/0... [1] https://www.cbsnews.com/news/titanic-visiting-the-most-famou...