I purchased this for a family vacation si I could snorkle and swim and not worry about leaving my phone and wallet on the beach.This bag handled that perfectly. I was skeptical at first and put it in a bucket of water for a few hours at home before I left with some napkins to test. I was dry inside after about 2 hours.When I first got to the beach on the vacation, I had my wife hold cell and wallet and went in for about an hour and when I came out it was bone dry inside. Now that I trusted it, I put it all in, and it worked great.It's a little larger than I'd like, but I guess that's not a bad thing I guess. The material is fairly stiff, it's like a molded rubber or a rubber coated cloth. The zipper can be a little stiff and comes with some silicone. Thisnactually put my mind at east that it wouldn't open up while swimming, so while it wasn't the easiest to open and close I believe that's a feature.Is it water tight? Yes, very much so. You do have to look to make sure the zipper is FULLY closed. I know that sounds obvious, but but if you're used to having a waste bag and haphazardly opening and closing it, it won't be waterproof unless it's FULLY CLOSED.You can use it 2 different ways, leave it puffed up full of air and it will float, push the air out before zipping it and it will not. You may not want it to float if you're snorkeling or swimming below the water and don't want the buoyancy. I got a bright yellow one to make it easier to see if it came off. I'll probably let it float if I'm canoeing or something where I'm not in the water, but take the air out if I'm swimming.The belt is also removable, which is a great feature to me. I'm a larger guy and most of the other bags I looked at were on the smaller size for me. You can change out the belt for a larger one, a more comfortable one, or a new one if the old one becomes unserviceable. I used a dive weight belt that fits me a little better.Overall I'm quite pleased with this bag as we're a few people I saw while on vacation who asked how to get one.If I could change anything about it, it would be to make a model a little smaller in addition to this one to be a little less obvious when not in the water but overall a great product.