arduino and proper proximity sensor

Hi guys. I want to use a proximity sensor and an arduino to know when a person is in the shower. What I have in mind if that if the sensor measures a range of distance it would mean that the person is in the shower. I have made some research and the infrared Sharp GP2Y0A21YK0F seems appropriate for the distance range I need that is around 20-60 cm depending on the size of the shower. However I am ignorant in this topic and I want to know if the water from the shower will make an interference when measuring the distance and generally speaking if this is a suitable sensor for my objective. Additionally, I read that the voltage output from this type of sensor is not linear, would it be difficult to actually know the distance?

Many thanks in advance :slight_smile: