Standing on a pebbled beach on the Greek island of Lesbos, Mehdi Salehi searches for a good spot to set his drone loose.

Far from being a hobby flight, this is a project to save the lives of drowning refugees, designed by a 33-year-old Afghan who was once one of them.

Fifteen years after fleeing his home to escape the Taliban, this drone expert wants to help others like him survive the perilous crossing of the Aegean and Mediterranean seas that has claimed thousands of lives.