The Canadian Forces doesn’t yet know where the wreckage of its Cyclone helicopter is but discussions have been held with the U.S. military about possibly using deep-sea submersibles in recovering the debris.
— Read on ottawacitizen.com/news/national/defence-watch/canadian-military-doesnt-know-location-of-cyclone-helicopter-wreckage-but-u-s-approached-for-help-in-recovery/

I’m surprised given our current sonar technology, that the debris has not been located. The real problem is recovery, as 3,000 metres is a daunting prospect.