Welcome to Android Central! Moved to the S7 edge forum. It's always possible that a component did in fact get damaged by water. Although they certify it for water resistance, they can't guarantee that the phone will be completely impervious to water damage -- it says this in the manual:
"This device is rated IP68 using the Ingress Protection rating system. Your device has been tested in a controlled environment and shown to be water and dust resistant in certain circumstances (meets requirements of classification IP68 as described by the international standard IEC 60529 - Degrees of Protection provided by Enclosures [IP Code]; test conditions: 15-35°C, 86-106 kPa, 5 feet, for 30 minutes). Despite this classification, your device is not impervious to water damage in any situation." (From the manual for the Verizon variant)