I had a similar experience last year at Labadee, although not with the rain added in thankfully.
We had 9:30 reservations for the zip line and it was VERY windy with the water all churned up. The forecast was for the wind to die down throughout the day so we were told to come back at 11 to see if they would be doing the zip line. When we got there at 11 it was still windy and they were turning some people away, but we did not know why at that time. They looked at my DH & I next in line and said we were OK to go, and before we knew it we had been through the mini zip line and were heading up to the top for the big one with a group of 15 people.
They asked the largest folks in the group to go first and told them not to sit up but to lie back flat like a knife so that they would make it to the platform at the end without the wind slowing them down. They made it no problem. The next group went, again the largest people that were left...they also made it but one or two got slightly turned from the wind. Now it was time for the last 5 of us to go and that is when I realized that they had set a weight limit of 150 to be able to go down. No one had asked my weight prior to the moment when they hooked my harness up to the zip line, and that is when they realized that while I am tall I only weighed 125 and shouldn't have been allowed. Another woman in the party was also "underweight". We were willing so they decided to let us go and they gave us some extra instructions on keeping the harness straight to not allow the wind to slow us down. They also put us on the lines closest to the beach.
Away we went and it was so-o-o much fun! I watched the 3 heavier people, including my DH, take off and go so much faster then the other woman & I were going and they all made it to the end. About half way down I noticed that the whirring noise of the zip line as we descended was slowing up and then we were both hit by a huge gust of wind that spun us all the way around, even while we were fighting the harnesses to stay straight. That killed all our forward momentum and we stopped, the two of us dangling over the white capped water, bobbing up and down on the zip line and waving to the folks watching from thebeach. Luckily for us it wasn't raining as you had. I actually enjoyed the wonderful view and got to know the other woman hanging out with me, LOL. They ran a long rope along the beach to where we were and one of the guys swam out to bring it to us, then they dragged us back. The zip line was closed the rest of the day.
I'd do it again in a heartbeat, and am actually looking for a cruise to book this winter that goes to Labadee so I can go again :) although this time I'd like to sit up so I can see LOL