A combined outing can contain several activities, but each takes time away from the others. Decide whether the priority is the water, a canyon walk or Dahab itself. Check that Blue Hole access is part of your selected option, since a low starting price may describe the base itinerary only.
Decide what matters most on the route
Keep the whole day available and avoid a fixed early dinner back in Sharm. Bring the original documents requested by the operator and a dry change. Ask about supervision for water activities and compare the actual stops before choosing by price.