We did ours on a Monday and almost risked not being able to swim with them at all. They weren't too interested in coming over at first (keep in mind you only get to swim with them as long as the dolphins want to do it), so the trainers instructed us to turn our backs to them because they hated being ignored. So we did that, and about a minute or two later, they came swimming over and were fine after that. I don't know if the weekend really has much to do with it, since they're pretty social creatures as it is. I do know that they said in all of 6 years (7 years this year), they didn't participate only 2 times (and I'm sure at least one of those times were with Toby & Bob...both of which have passed away).