As if I don't have enough equipment already and I use all of it-lots of scuba gear, diver propulsion vehicle, commercial and non-commercial side scan sonar systems, a boat.... however an ROV makes alot of sense to me and it's not the first time I have pondered buying one. Shocking I know.
Commercial systems can easily run hundreds of thousands of dollars and weigh so much you need a crane to get it off the deck into the water. Much smaller commercial systems such as the capable VideoRay product and other makes are available too.
Then you have systems like the Open ROV project, among other ones you can buy for short short money, relatively speaking. I am looking them over now for a possible purchase over the winter. Hardly a done deal but they are so useful it is a very compelling piece of equipment.
One system is here:
http://www.openrov.com/
One user of this particular system was hunting a neat old 53M steamer deep in Lake Tahoe and found it-some video clips can be found here along with other information:
https://openexplorer.com/expedition/returntothesstahoe
I have two targets in Winnipesaukee I found on sonar I have yet to dive that an ROV inspection would be really useful to have prior to the dive, oddly enough both at 106 feet.
One is definitely a vessel and the other definitely man-made but I cannot say exactly what the 2nd one is.
Not sure what if anything I will buy for an ROV but time will tell.