I loved to swim! When I first had my operation, I let it go. I wouldn't go near water in fear the flange would come loose and float off into the wild blue yonder. I did find a few tricks that worked for me.
First, I use the Skin Prep wipes and spread it around the band-aid part of the flange that helps with a barrier on it. I also use surgical tape along the edges for added security. As for the bag getting wet, I wear Hollister 2 piece that has a felt-type covering on it. After I finish my swimming, I just take a towel and rub the felt part and even use a hairdryer to dry it up in no time. I often can go a few days swimming several times a day with no problems. Of course, I also do the "I'm due for a change tonight so I'm staying in the water allll day" thing too.
When I'm at a friend's cottage and in the lake swimming, I really couldn't care should anything fall off....but when I am at a public pool, I basically stick to just wading in and out, no fancy dives or that sort of thing. I go swimming in my ex's building pool with my boys quite a lot, and that is a saltwater pool and still things stay intact.
Remember, YOU are the boss, not your stoma or your appliances...ya got to SHOW that appliance who the boss is!! GO FOR IT...DIVE IN!!! (pun intended!)