People read their phones on the toilet - probably every single modern phone user has done it at least once. It is not inconceivable that a small, but significant, number of them have fumbled the phone and it has fallen into the bowl.

Likewise, pools, beaches, and boats are places people are very likely to go with their phones in tow and in use. It is not unlikely some of those - one can assume - millions of instances have produced some contacts between phone and water.

I ride a motorcycle and mount my phone on the handlebars for guidance. I spend a lot of effort keeping it dry and have actually lost a couple of USB cables (but not the phone, thankfully) to damp.