Just wanted to clear up some points in this thread however am very limited what I can say for now.
There is no problem with the avaliablity of the equipment to undertake this workscope. There are a number of suitable vessels currently idle with 4000m rated WROV's spreads on board and ready to go. There are only a handful of suitable deep tow side scan sonar systems around but such a system is indeed avaliable right now. Basically there are no 'equipment issues' causing these delays, I could have a vessel fully mobbed and ready to go in 10-14 days.
The technology above stands a very good chance of finding the boxes, I have seen the resolutioin that this sonar system produces and trust me it can find very small items down to 6000m. Temperature layers are also not a problem, the sonar fish is flown 100m or so above the surface of the seabed and covers a very wide swath, the main problem being the terrain it will need to be flown over.