Just look up "floating phone pouch" on Amazon. I went kayaking a little while ago and in the office they were selling these. Some have IPx8 rating. You can still take photos or use your phone, through the plastic, and if you drop it in water it will float on the surface.
This is similar to the one I picked up.
I got one off amazon and reallllly glad I did. Saves me a ton of time. I also use it during packing up to blow off sand from the board and my gear/feet. I also got an inexpensive BT radio that is waterproof. It works surprisingly well! I'll link both (if possible), I tend to go overboard researching everything before buying so figure might as well share the spoils lol
BT radio (also plays FM/AM big plus for me):
Watertight phone pouch: