Trekking trips on foot, by camel, jeep or even llama are available. The Maktesh Ramon crater in the Negev is a popular area and guided treks are particularly advisable in the desert regions. There are lots of walking trails in the Golan Mountain and around Mount Hermon in the north where, amazingly it's possible to ski in winter. Israel has a great variety of National Parks.
Diving and watersports
The best diving and snorkelling is in the Red Sea Diving with easily accessible coral reefs. There are a number of diving schools at Eilat offering courses for beginners and trips for the more experienced, as well as classes in underwater photography. At Caesarea on the Mediterranean you can dive the ruins of Herod's city. This coast has opportunities for water skiing and windsurfing. A range of water sports is available on the Sea of Galilee where it's easy to arrange tuition and equipment hire. Use your international cellular phone rentals to make diving reservations.
The Mediterranean coast has some good swimming beaches but because of the sometimes strong undertows, it's safest to swim where there are lifeguards. Pollution can be a problem in some areas and stinging jellyfish are common in the summer.
Rafting and canoeing
In the north, rafting and canoeing are available on the Jordan and Banias Rivers. The Jordan River passes through some beautiful scenery and nature reserves. Many Kibbutzim in the region arrange rafting trips.
There are lots of places where horse riding is popular. Stables and riding schools are located throughout the country, but particularly in Upper Galilee, the Golan region and on the coast between Tel Aviv and Haifa. Use your Israel mobile phone rental to get more info on horseback riding in Israel.