In that unlucky case, some other kitesurfers may help you. But in the worst case someone would have to call the coast guard to help you. That’s why you shouldn’t go alone in challenging conditions ;)
It is worth adding that there is a local rescue service (not coast guard) with 2 or 3 speed boats roaming the coastline to collect surfers having trouble in offshore wind. However the service is quite costly unless you "book" it in advance (which is possible in many surf shops in Tarifa).
