When we went on this cruise a few weeks ago, they were no longer offering the day trip to Marrakesh, so it may well not be an option. We booked the excursion to Taroudant, which is much nearer and supposed to be a 'mini-Marrakesh'. Unfortunately, we could not dock due to high winds, so I am unable to tell you whether Taroudant is worth visiting! However I understand that the drive from Agadir to Marrakesh is extremely long and tiring, so this may be why it was withdrawn.
That's really interesting and helpful - perhaps there may be others who managed to get to Taroudant. I hope you enjoyed the rest of the cruise. Win.
Yes, we certainly did enjoy the cruise. I have left a review on this site. I hope you have a great time too!