Contrast for…

Four ways people use it

The app is the same in each case. What changes is which part of it matters, and which limits you are most likely to run into.

• Contrast on Apple Watch Ultra On Apple Watch Ultra, Contrast starts the round when you get in and reads the water. Ultra is also the one watch Apple allows in a cool sauna.
• Contrast for a cold plunge at home Contrast logs any tub, barrel or bath from your wrist: the real water temperature, heart rate per round, and Apple Health, with no hardware login.
• Contrast for heat acclimation Contrast measures heat strain at the same temperature over months and estimates acclimation from your recent heat days, with the evidence labelled.
• Contrast for hot tubs and hot baths On Apple Watch Ultra and Series 10+, Contrast detects a hot tub or bath from the water, times it in bands and sets it against the bath studies.