Medical disclaimer

Nothing on this site diagnoses, treats, or prevents any condition, and it is not a substitute for advice from a qualified healthcare professional. The calculator's outputs are estimates from a general model — they cannot account for your individual health.

Cold-water immersion can trigger serious physiological responses, including: ^[1]

• Cold-shock response — an involuntary gasp and rapid breathing on entry that can cause water inhalation and is a leading cause of sudden drowning.
• Cardiovascular stress — cold causes a sharp rise in heart rate and blood pressure, which can be dangerous for people with heart conditions.
• Hypothermia and after-drop — core temperature can keep falling after you get out, leading to dangerous cooling if you stay in too long or don't rewarm properly.
• Impaired function — cold quickly reduces grip strength and coordination, which matters in open water or unsupervised settings.

Get individual medical clearance before any cold-water immersion if you are pregnant, or have or suspect heart disease, high or unstable blood pressure, a history of stroke, Raynaud's, diabetes, a seizure disorder, or any serious chronic illness. When in doubt, ask before you get in. ^[2]

Never plunge alone in open water, never combine cold immersion with alcohol or drugs, enter slowly to blunt the cold-shock response, and get out at the first sign of feeling unwell. Rewarm gradually rather than jumping straight into a hot shower.