I also dream a lot of slides. It would depend on the dream action and other factors present but generally would be about feeling of loss of control, this may be a welcome loss of responsibilities (if ride down enjoyable) or generally feeling as if control has been taken away from you undesirably so if the ride down wasn't enjoyable. Water on the slide relates to financial matters. Loss of financial control anticipated. Or freedom from financial obligations. So can be good or bad omen depending on other dream factors. In your life, you feel you need to gain more control over things in general, not just financial. This may be a 'real' factor or for you just a 'perceived' need, a driving force.