This is my first attempt at any type of Garmin application. I like to paddle outrigger canoes and there's been several times where I've completely lost visibility while on the open ocean. So I came up with this datafield that you can add to your application that allows you to either set a waypoint at the start of your activity (just enter 0, 0 for latitude and longitude) and navigate away and back to that point. Or you can enter a single waypoint so you have a reference vector to that latitude and longitude position.
In addition it computes your velocity made gode (VMG) which is a key indicator of how fast you're moving towards or away from your waypoint. This is important in water sports because currents can set you in different directions and if you navigate just by sight your not necessarily going to be following the fastest heading back to your goal.
It's a bit of a complicated subject so I created a video too to explain it some. Check out my app and let me know what you think. I just recently updated it to include most of the garmin devices.
https://apps.garmin.com/en-US/apps/e486c0c9-ba0c-4197-925b-a21bc65806f5
I've been using it personally for quite a while now and I've found it very useful. In fact the cover "hero" image is from a race that had a squall roll in (it's not photoshopped) and this datafield kept me on course while others ended up lost until the rain cleared.