How to use apple watch for winter open water swimming

I tried to use my watch for a Swimrun yesterday and in the swim section it just paused. I had my watch on my wrist over neoprene wetsuit so I guess it was because it couldn’t detect heart rate. However this is a problem as when it gets colder I will have gloves on too and want to see my watch to check how long and how far in the water. Is there a setting on the watch that will do this? Last winter I had a Garmin watch and it was very happy recording a swim whilst outside my wetsuit.

Thanks