Over 100 Containers Lost

The Canadian Coast Guard indicates that they have only located 4 containers of 109 lost from the Zim “Horizon” off the coast of Vancouver Island.

Of the 105 containers unaccounted for, two containers were loaded with the same hazardous material the was attributed with causing the spontaneous fire onboard the vessel.

I presume these lost containers sank and are therefore no longer a hazard for shipping in the area. Wouldn’t it be nice if we knew this with certainty? How hard would it be to add location finding technology to containers to aid in such events?