You can do the parasailing without a platform and winch, but you still
needs
gobs of HP! And a bigger boat. Years ago, we did it with a tournament
ski
boat and beach starts. But with a big wind, the boat would be pulled
backwards at times.

So, you can see that the pull on the towline is more than you might expect.
People have been killed when the towline breaks and the hapless parasailer
is dragged through a beachfront area by the winds.