The latest report to add credence to these rumours comes from tracking site Zauba (via SamMobile), which claims to have a list of the devices' components.
Listed parts include a waterproof mic and a SIM tray on both devices, and waterproof tape on the Galaxy S7 Edge - both handsets sound capable of making a splash.
It's unclear whether the latest Samsung flagships will be fully submergeable, but water-resistance looks like a given.