It's becoming more and more common these days to see armadas of stand up paddle boards plying the waters of the Ljubljanica during the spring and summer months, and one of the organisations leading the way (both figuratively and literally) is the ASI accredited SUP Klub, based at Livada, just south of the city centre. They offer a variety of private and group courses, as well as tours for all kinds of groups, short- and long-term board rentals, and even Sup Yoga. However, visitors will most likely be interested in one of their scheduled twice daily tours during the season: the Ljubljana Urban City Tour, which takes in the many sights along the riverbanks through the old town, or the Ljubljana Green Tour, which heads in the opposite direction upstream to explore the flora and fauna of the UNESCO designated Ljubljana Marshes. Lots more info can be found on their website.