Can Layla swim? I bet boxer would be really good at it, especially the "high jump" one instead of distance. Definitely a sport dominated by labs and -doodle crosses (at least in my area), but it looks like a lot of fun. I have a friend that does the annual Dock Dogs event in our area and her golden-doodle has a blast.
I can picture JOhann jumping in, starting to drown, then me having ot save him.
I've seen a few dogs do the event with lifejackets on though, so that might be an option.
Have fun! I'm always trying to find new things to do with Johann to keep him amused (still sidelined from agility due to my injuries). I may try a tracking clinic with him next month, and want to do a beginner weight pull class soon too.