Viator advises that you confirm your trip at least 48 hours before the trip. I contacted the tour operator and spoke to their staff. She told me to go to the tour desk in the lobby of the hotel I had booked to stay in. I explained that I was in Florida and would not arrive in Jamaica until the day before the trip. I ended up contacting the Viator customer services when I realized she was unwilling to help. Viator assured me that the relevant paperwork would be at the concierge desk; when I arrived this was not the case. Fortunately the tour Rep on site was sympathetic and arranged our pick up for 08:30 the following morning.
On the whole it was a good trip. The enthusiasm and good spirit shown by the tour guide is to be commended.
The downside to the trip was the time allocated to shopping. Three 40 minute stops that included two shopping areas and a craft market. An additional stop (30 minutes) for refreshments and rental of water shoes (bring your own) and finally a stop at a "all you can eat Chinese restaurant (US$15/person).
When we eventually arrived at the falls we were only there for an hour. The highlight of course was climbing the falls. The experience was enhanced by the guides that work there. In addition to leading the group and ensuring that we were all enjoying the experience, they carried our cameras and took some awesome photos for us.
I whole heartedly recommend this experience but suggest taking the half day tour if you want to enjoy the falls and beach at Dunn's river. If you are into shop, shop, shopping, then this is the tour for you.