The first thing I did (and the first thing you should do before using the camera underwater and each subsequent time before you intend to use it under water) was to test the seal. To do this I removed the camera from the case stuffed it with tissues and weighed into down in a bucket of water (otherwise it floated) for about 15 minutes.
The seal on the case won’t last forever and it will eventually need to be replaced, especially if used regularly in strong direct sunlight. So by testing it before each time you plan to use it underwater you will improve the chances of finding fault before it has a chance to damage your camera. (This sort of stuff should be in the manual, but sadly it isn’t).
I am glad to say with this somewhat limited test (the only thing I can do short of a 60 mile round trip to the sea as I suspect trying to sneak the camera along to my local pool would result in porridge for breakfast) all was good and the paper towels were dry upon being removed.