The Marion County Park is the farthest public up-river location to begin River tubing. During your float, all you do is sit back and relax! The Rainbow River is formed by a first magnitude spring that is ranked fourth in the state for volume of discharge. The Rainbow River is a gently winding river that is 5.7 miles long and merges with the Withlacoochee River at Dunnellon Florida. They crystal clear water, abundant with fish, wildlife and vegetation along with the constant water temperature of 73 degrees, has attracted a number of modern day activities, incuding the spectaculair river tubing.