Create a custom activity/app

Hi guys!

I spend most of my free time training in triathlon and I run into a problem. Swimming distances are quickly wrong as soon as you practice the technique ...


As an engineer, I love challenges and would like to solve this problem. The goal would be to have the app that you normally use by clicking on start button, but but with a little extra: when saving the activity, you should be able to change the distance of each lap (before saving or exporting to garmin connect).


I have a good experience of computer development with several technologies but I have never developed anything for garmin so I do not know how to start to even overide the swimming application.


Do you have any leads or resources to share with me?

Thank you in advance,
Stéphane;)

PS: I own a fenix 6 pro and a forerunner 245.