Quantum Wireless via Amazon offers Prime members this Waterproof Case for iPhone and iPod Touch for $9.58 plus free shipping. (Non-members can spend $25 or more to qualify for free shipping; otherwise, shipping costs $5.58.) That's $1 under our January mention and $1 below the lowest total price we could find for a similar case elsewhere. It protects against water up to 100 feet, while still allowing full use of the device (including the camera). It's designed for use with the iPhone, but works with other smartphones and electronics.

Amazon Prime membership is $79 per year; however, Prime is free for college students for six months, and free for parents and caregivers for three months.