I was very surprised to come across Super 8 Sound film for cameras available again. The seller in the UK is The Old Film Company, and each cartridge costs £89.99. That's the good news, now for the bad. The seller says that that they are keeping in the occasional organic watermark and other defects associated with real film. In the past I shot kodachrome, Ektachrome, Peruchrome, Agfachrome, and Orwo B&W. I never had water marks on my films. The seller has posted a video on Youtube; apart from the awful colour, I should be very disappointed if my films came back looking like this.
https://www.youtube.com/watch?v=vwc3RDaLTUghttp://theoldfilmcompany.com/Page4_20.htm