I just purchased a 2008 Sea-Doo Challenger 180. I love the boat, but when I try to pull people on a tube I find them getting drugged underwater, why? If I hold the rope up until they get going it will stay afloat, but once it catches it wants to pull the tube back under. My old outboard boat I just hit the throttle and went, is there something I am not doing right? Do I need a tower? PLEASE HELP!