Scosche Rhythm 24

I am considering to buy a additional HR monitoring device - Scosche Rhythm 24 (say 'R24' below).

Before I decide to buy it, I need to ensure my required features can be provided by R24.

I have a Garmin watch Forerunner 935. I am satisfied all the basic functions it provided, except lack of the recording heart rate function underwater.

I have no plan to buy chest heart rate monitors, I believe I will feel uncomfortable during exercising. Also no plan to buy new 945, it is over my budget. Instead, R24 is my current best choice if it really has the following features.

1. Record heart rate and distance when I am swimming.
935 is unable to record HR underwater. If I have R24, when I go swimming, should I need to be wear Garmin watch and R24 on the same arm, regardless of indoor or outdoor swimming? Could my 935 be able to record distance & HR at the same time underwater if I have paired R24?

2. Could I directly migrate the swimming activity record to Garmin watch, then sync to Garmin mobile app?
Could I only wear R24 during swimming, then migrate the record to Garmin watch? If yes, how Garmin watch to process this data? Will it be treated as the same recorded by Garmin watch?

Many thanks!

[I know there are some testing reports for Garmin & R24, but mostly in English. I am Taiwanese and my English not good, and also there are only few old testing reports in Chinese. I feel hard to understand those reports, especially those reports like to use many technical terms to express. Of course I am welcome if someone can reply me in Chinese :)]