Earphone Plugs are a great way to protect one of you're most valued assets!
Most mobile device manufacturers have built into their products a "environmental sensor" which detects any contact with liquids. If the sensor is triggered it turns red which can cause device faults and failures.
If this happens to you then it can void your warranty.
Why not plug in a headphone jack plug or earphone jack protector plug for less than the cost of 2 coffees??