You shouldn't have problems with the wafer failing with a shower/swimming/bath.
Do you use Skin Prep of any kind? If you do keeping that to just the area around the stoma should prevent the water failure issue.
You can also try Sure Seals :
www.alpglogal.com you can go to that site and request samples.
They are a waterproof/breathable membrane that goes over your wafer to maintain it's integrity.
Personally, I shower daily (sometimes multiple times) and am very active/athletic, without wafer failing.
Also, another note: The most directions in the box with your wafer say to not get them wet for 24 hours.