One of my favorite hikes in Israel is along the Nahal Yehudiyeh in the Golan Heights. You have to swim, and in non-summer months the water is a bit chilly. But it’s an exciting hike in many ways.
Arutz-7 has a story which includes the details you need to know before you go. One sample:
Hiking the upper section of Nahal Yehudia is considered to be appropriate for good hikers who can swim, as there are a couple of places where you have to climb down the rock face with the help of handholds or a ladder into a deep pool that you have to swim across. Note that you must start out on the well-marked trail by noon.
The hike starts above the wadi on the red trail, walking through a deserted Syrian village of basalt field stones built on the remains of an earlier Jewish town from the Roman-Byzantine period.
Remains of a wall have led archaeologists to suggest that Yehudia is Soganey, one of the three fortresses (the other two are Gamla and Sele’ukya) in the Golan built by Josephus at the time of the Roman Revolt.
I don’t know how easy it is to find any more, but a great resource for adventures like these is the book by Joel Roskin, Waterwalks in Israel (Jerusalem Post, 1996).
UPDATE: The author of the article, Shmuel Browns, has commented below. Take a look at his website for a more comprehensive article and photos.