In an immersion suit, after 6 hours in calm water with temperatures between 32°F and 35.6°F (0°C to 2°C), the body’s core temperature is designed not to fall by more than how many degrees?

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The key idea is how an immersion suit limits heat loss to keep the core temperature from dropping too rapidly during long, cold-water exposure. In calm water around freezing, heat loss happens mainly through conduction to the water and some evaporation. The suit traps heat and adds insulation, so while the body continues to lose heat, the rate is slowed enough that over about six hours the core temperature is designed not to fall by more than a small, manageable amount.

That modest drop—about 2 to 5 degrees Fahrenheit—reflects a balance: enough protection to prevent rapid cooling that could impair judgment or motor function, but acknowledging that some cooling is inevitable in such harsh conditions. The water temperature range given (32 to 35.6°F) corresponds to near-freezing conditions, where this level of protection is what the suit aims to achieve.

If the core temperature were allowed to fall more than that, the risk of severe hypothermia and loss of capability would rise; if it were guaranteed to fall by less, the rating would imply unrealistically optimistic protection. The stated range fits the practical performance of an immersion suit under six hours of exposure in near-freezing water.