I've never gotten seasick in my life (I've spent days at a time on a small boat) but 25 min on the Frying Pan and I felt awful. If you get even a little motion sick don't do it.
They don't call it the frying pan for nothing. This place gets really hot, with black rubber flooring sucking up the heat of the day and throwing it back at the crowd.
ignore the crowds, you can get a peaceful open table any time of night by climbing the ladder at the fore of the ship. even when the bar is packed, this will be empty