The ferry from Sfax
The only way to get to Kerkennah, other than by hijacking a yacht or a helicopter, is by ferry from the port of Sfax. Ferries take just over an hour between Sfax and the harbour of Sidi Yousef, and the journey is one of the best bargains in the world...0.65TD (April 2007: GB£1 = 2.5TD).
There looked to be at least a dozen sailings a day, so the best advice is just to turn up in the port and chances are there'll be one leaving within an hour. If you do have to wait, there is a snack bar in the waiting room, and a couple of nice outdoor cafes overlooking the port and the modern trendy district of modern Sfax just 2 minutes walk away.
Coming back, buses leave Remla in time for the ferry...once you arrive in Sidi Yousef, you have about half an hour to buy your ticket and have a glass of tea.
Most of the locals rush on board to find seats inside the ferry, next to the snack bar (tea and sandwiches...), but in nice weather, the upper deck is quite popular. In bad weather (and my first crossing was windy, misty and quite rough), you'll only have to share the deck with a few hardcore smokers. Things to look out for en route include Sfax's phosphate mountain, and the local Kerkennian offshore fishing traps.
Nearly all the islands' yellow taxis wait at Sidi Yousef for the boat to arrive. They act as louages, and all follow the same route (there is really only one direction you can go in Kerkennah!), and you only have to bother asking if you're heading to Sidi Frej or one of the off-road villages like Bounouma or Kraten...otherwise, just pick any one and wait for it to fill up. The journey to Remla costs 1TD, ridiculously more than the ferry!
You can flag down these taxis anywhere on the island...they run mainly between Sidi Yousef and El-Attaya, passing through Melita, Ouled Yaneg, Ouled Kacem, Remla and El-Abbasia, although they will take you to Sidi Frej or the eastern outlying villages on request.
Walking is a good way to see part of the island....my 15km walk from Remla to Sidi Frej and Sidi Fankhal is easy to do in either direction, although take plenty water as there are precious few shops on the way.
Cycling is also good, as long as you are prepared to do battle with the wind, as the islands are extremely flat. My hotel rented bikes for 5TD a day, while the hotels in Sidi Frej charge a bit more. Every village has a bicycle repair shop.