I suggest upgrade to the phone .... you'll be amazed at what other improvements you get besides a better camera ..... (I just upgraded from an iPhone 5 to an XR and I'm asking myself why did I wait so long???? Better reception, apps have improved functionality AND run faster, battery lasts WAY longer)
then a bag from AMAZON ..... I bought a pack of 4 for $13!!!!! And they work great .... for snorkel/surface use.
Smartlle Waterproof Phone Pouch, Universal Waterproof Phone case, Dry Bag Outdoor Beach Bag for iPhone 11/11 Pro/11 Pro Max/XR/XS Max/X/8 7 6S Plus, Samsung Galaxy, LG, for All Phones, Luminous-4 Pack