Topic has been covered before (few years back).
The ESDS is the smaller of the Shark Defence Systems, developed in Hawaii in I think 2012.
Roughly the size of a match box and is contained within a leg rope type strap.
Its competition the Shark Shield has a trailing electrode, is bigger but probably more powerful.
Doing research the ESDS Company has split and now two systems have developed. "No Shark" will soon be available in Australia.
I understand the ESDS has had warantee issues?
It seems the most proative solution to isolated surfing locations.
I laughed at the FAQ on the web site "Will it stop shark attack" I ****n hope so.
Interested to hear from owners if they have had problems with the units or / and especially if they've had shark encounters??
Cheers Mike D.