White water rafting (Istanbul)

I want to go white water rafting with some friends from IN but I am finding that it is a hassle with the renting of the bus and paying extra for insurance. Can I just get together with whoever is interested, pile into a few cars, and head to Duzce. This way we would only pay Protected content , unless someone wants to negotiate that down, take cars, no one is the "organizer" (therefore arranging a bus and paying for insurance), and just go and have a great day.
IS THIS PROCESS POSSIBLE IN TURKEY?????
PLEASE ADVISE.
I want to go on the first weekend in May, before the river is too low.