Egadi islands are a set of three little island situated on the very west coast of Trapani, they are part of a maritime natural reserve.
Favignana: Located about 17 kilometers southwest of Trapani, this is the largest of the Egadi, or Egidean, Islands. Still known for their tuna (tunny) fishing, these islands are now famous as beach resorts. Favignana, in particular, is a favorite spot for Sicilian sun worshipers. The ferries from Trapani arrive at the port city of Favignana, from which transportation to the other islands (Levanzo, Marettimo) is available. Most of Favignana's beachgoers are Italian; it seems that few foreign visitors venture this far.
The best deal and fun is renting a boat in 'Marausa' which is a little sea place 20 kms far from Trapani, you can have a boat for 4 people all the day for only 70 euro including 20 litres of petrol.
But if you go by boat then be sure to remember where you come from, take something as referement point, it might be not that easy to find the spot where you left from, when you are in the open sea the coastal details become smaller and smaller. Have fun!