When driving to Drake Bay most of the streams are small and are rarely, if ever, a problem for a 4x4 vehicle to pass.  The last river that you cross before coming into Drake Bay is an exception.  This river is named, "Rio Drake" and you need to cross this river in route to Drake Bay. The problem come with this particular river is that it can rise very quickly.  The river water comes from springs and rainwater that originate in the mountains.  The springs constantly flow assuring that the river never runs dry and the rain from the mountains is what causes the river to raise the most drastically.  The good side of this is that the water will regress quickly once the rain has stopped (in the mountains) for approximately 4-5 hours.  The gravity of the high elevation pulls the water to lower elevations and then pushes it out into the ocean.  This gravity causes the river to run with a sometimes very powerful current.  While a large tractor could possibly overpower the stong currents, it is still very dangerous to try due to the large floating debree. Trees and branches that fly by at high speeds are like missiles. The only answer for this uncommon weather experience is to simply wait it out.  An average amount of rainfall will not cause this situation, however, rainstorms lasting more than a couple of days will.  If a short but heavy rain comes and causes the river to rise higher than you feel comfortable driving through, you can contact "Victor" who has a large orange tractor.  He will place a plastic bag around your exaust pipe and pull you across. 
All replies will be sent within 48hrs (internet connection permitting)