NUOSWEK Digital Timer Waterproof Shower Timer with Magnet and Large LCD Display (Waterproof 7 Key)

The most useful rule for a first cold plunge is to decide how long it lasts before getting in. A timer keeps that decision for you. This NUOSWEK is a small square unit, about 3 in (7.6 cm) across, with a large LCD and seven keys. Four of them add time – 10 minutes, 5 minutes, 1 minute, 10 seconds – so setting 30 seconds or two minutes takes a few presses, even with cold fingers.

The listing says it withstands spray from any direction and also says not to put it in water, so it belongs beside the tub, not on the rim. It has a magnet and a hanging hole; next to a fabric tub, the hole and a hook are the ones that get used. When time is up, the alarm runs for 30 seconds and stops by itself.

Tip: Hang it at eye level where you can see it from the water, and press start as you step in – not once you have settled.