Standards - Most smartphone “waterproofness” is rated IPX7 which is really not adequate for extended immersion. The charging ports are particularly vulnerable. Even if your phone continues to work, you may have issues with getting the charge port dry enough to work for recharging. It is highly advisable to use a clear, waterproof case with IPX7 rated phones.
Cases
Most soft cases are variations on the same quite cheap designs (most likely from the same manufacturers who just relabel them for the various retailers). You should do an initial waterproofness test to make sure they work. And it is unwise to assume that they will continue to be waterproof for a long time. Periodically test them and/or replace them on a fairly regular schedule.
Phone Usability in Cases * think twice before you assume that you can use your phone for help in big conditions, particularly in cold water. Test it and Practice Using Phone in Case particularly if you ever rely on a phone solely without carrying a VHF radio also.
The case has to be clear enough to easily read display
You want to be able to get enough air out of the case before sealing so that your finger taps and swipes will work on the phone through the case
If you are relying on phone for safety: Test speaking and hearing through case. How rough can the weather be while still retaining the possibility of communicating effectively with your phone?
Mounts
Apps
Training
Wahoo Fitness
Safety
Emergency Beacon IOS only, at touch of a button will send GPS coordinates to pre-programmed destinations, text, email
SafeTrx android and ios app that allows on water group members and on land friends to track group members. More extensive support is available for Search and Rescue services with licenses. But the standalone app works for the group tracking between personal phones carried by users on the water.