The last time we did this, the operator's asked us if we wanted to be dipped or not. My DH and DD went up together and they were dipped to waist level, I went up next and said I only wanted my feet to get wet and they stuck to that as best they could. One guy asked to go really low and they dipped him to about shoulder level, one or two ladies said they didn't want to get wet at all and they were brought directly on board at the end of their "flight".
With regards to weight restriction, our DD was too light to go up on her own. The combined weight with my DH would have been around the 250 lbs mark. We had one person on our speedboat that was closer to the 280/300 lbs range but I'm not sure what the maximum limit is.