Here is a small sample video shot with my Galaxy S20 in one of these waterproof phone cases.
Before my wife and I set out to visit the incredible city of Savannah GA for a late summer vacation I bought this two pack of waterproof phone case for $10 on Amazon. Before we go any further I want to make it clear that I'm not being paid to write this. These very inexpensive cases worked amazingly! I've posted a video below of myself playing in the Atlantic Ocean waves on Tybee Island.
The most important thing is obviously that they don't leak. They passed that test with flying colors which is great because so much of what we do these days is phone dependent and while I could have found my way back to the apartment we are renting it would have been really upsetting if I needed to get a new phone and to have had to explain it to the sales person why.
One other measure that I think is important if you're looking for a waterproof phone case is it's ability to function. While I did have some issues double-clicking my power button (how I typically turn on my camera app) the screen worked very well. In fact it worked a bit too well as the salt water in the ocean managed to close a the camera once.
The downside to these bags was that holding the phone in a way that allowed me to shoot video or take photos in the water or even underwater meant that my finger was very close to the camera lens and several times ended up in the shot. Holding the bag is otherwise easy and despite some really sizable waves smacking right into the phone I managed to hold onto it. But they also provide some straps which I didn't bother using so I can't say how effective they are.
The final note I'll leave about these is that they managed to capture sound really well too so when you're shooting video on your phone you'll hear everything which is really great. I have a large waterproof case for my professional cameras that muffles the sound but since I don't shoot a lot of video underwater with them it's not that big of a deal.
I hope you find this review of these inexpensive waterproof phone cases helpful. If you'd like other fun little tips like this consider signing up for my mailing list and get regular updates about cool products like these and tips to improve your photography.