You can take your phone with you! On the water or in the water, this is the best dry bag for your phone. The double magnetic seal prevents water from getting in even when snorkeling at depth. This is a favorite of our staff, and we use it on the water all the time.
Go Bags are awesome, I've used them whitewater kayaking, snorkeling, and diving, and never had an issue. It's a solid way of taking photos or videos with your phone while in the water. My protip offer is to add a float and replace the string connecting the bag to the lanyard with something more robust.