You can pee, poop, swim, sleep, do whatever you gotta do - FLEX disc will stay out of the way!
Just note that if it leaks when you use the restroom that's totally normal and nothing to worry about.
FLEX disc will push part way out when you bear down and relax your pelvic floor but pops right back into place when you're done. If it feels like it hasn't gone back into place, just use a clean finger and push it back up behind the pubic bone. You can also opt to do a kegel instead.