I paddle sprint vessels on the water; so a little more advantageous due to having something to attach the GPS devices. I'm adding an answer because the three devices I use have proven helpful in getting data and perhaps might be helpful to you with just a little adaptation.
Device 1, Garmin Foretrex 410.
This is way cheaper than the Fenix but well proven on the battlefield. I once dropped in the water (3ft) after a paddling session & didn't know until I found it again two days later upon returning to the river. It continued to work without any issues! I use this for speed & distance feedback while paddling. Kind of real-time feedback. Yes, there is a lag but you get to know what it is and it works to give you a very good sense of your current status. It is very helpful during sprint pieces to allow you to see exactly where you peak. It is responsive and reasonably accurate.
Device 2, Garmin Forerunner 235.
I use this on my wrist mainly for tracking heart rates for intervals and for tracking data to review later. It also has audible cues for intervals. This device is also older & cheaper, but very useful for both real-time heart rate & for reviewing workout graphs.
Device 3, smartphone.
For interval audible cues & tracking apps to review after the session. I put the phone in a tight-fitting waterproof pouch with a floater. Always add some floater to your valuable, regardless if they're waterproof. They'd be useless lost on the bottom of the water.
These three devices, plus a camera, have helped me train well with sufficient data for (almost) real-time, and for later review. I've been using them for many years (the Forerunner watch is more recent but the Foretrex 410 has been with me for 6-7 years, with the 301 before it, adding to nearly a decade of good use).
How to apply to your case:
Suggestion 1. Get an elastic strap from any fabric store the same size as the wrist band and loop on the watch to wear across either your back near shoulders or the back of your head. Since you swim head out of the water, this might work, or
Suggestion 2. Wear a cap that has a bill (a baseball type cap). Maybe even get one with a clear visor/bill. You can attach your watch to the bill via some simple configuration. You can even cut two openings on the bill just far enough apart to loop the watch band around the middle of the bill that will allow you to see its face & data. Attach the band through the slid-openings & voilà, you've got a working solution. Be careful as the cap can sink fast if you hit a wave or the wind blows it far from your reach. I've lost a few through the years in rough water or wind conditions. My solution is add something to help it float. It doesn't need much, even a fishing bobber will keep it dangling near the surface. Of course, test it out first.
Suggestion 3. Secure it to a small flat piece of wood or foam with a string and drag it behind you. It's a little awkward but I believe still better than changing your stroke techniques.
Hope one of these can be helpful for you. Enjoy!
