Pick-up at the airport of Agadir (there and back) is available for a total of 30 €.
CTM runs several times daily from Marrakech to Agadir for about 10 € pp. plus 1-2 € for the luggage. The buses are good and even air conditioned: www.ctm.ma/en
The bus stop is located on Rue Abou Baker Seddik, just south of the train station and a few minutes walk from Marrakech train station.
Another option is Supratours: http://www.supratours.ma/en/
Get a cab at Agadir airport and drive to Aourir. Depending on traffic the journey takes about 40 minutes and costs between 300 and 400 DH (about 30 €). The price varies depending on your surfboards, how many people are joining and how much luggage is there in total. It is important to set the price before departure with the driver! If you travel alone it is best to approach other people who are also looking for a taxi so that you can share the travel costs. If you bring a surfboard don't forget to bring straps because not all taxis have them.