Hearth rate alert during Pool Swim

Hi

I would like to be abler to setup a alert to warn me that my hearth rate was below a certain value or bellow a zone. I would like to use this because when I stop swimming to rest a little I would like the watch to alert me that my hearth rate is in a rested zone and I can start swimming again.

My 165 only has alerts for time, distance and calories. Can you please add the possibility to create alerts based on the hearth rate zone?

Best regards