The thermal insulation in two types of diving suits were measured in cold water. One was dry suit that had been used in the Antarctic sea and another was wet suit for use in marine sports.
　The wearing conditions of the diving suits were as follows.
　Experiment 1, Dry suit (Neoprene 6.5 mm) + Under wear (wool)
　Experiment 2, Dry suit (Neoprene 6.5 mm)
　Experiment 3, Wet suit (Urethane 3 mm)
　Wet type diving gloves (Neoprene 3 mm) were worn in all experiments. Water temperature was 3°C and immersion time was 60 min in experiment 1, and 30 min in experiment 2 and 3.
　The results were as follows.
　1. The thermal insulation of the diving suits was 29% higher in experiment 1 (dry suit + under wear), and 45% lower in experiment 3 (wet suit) than experiment 2 (dry suit).
　2. Compared with wet suit, body temperature was well maintained in dry suit (experiment 1, 2), but the hand temperature was much decreased and subjects felt numbness in their hands in all cases.
　3. Agility of the hand decreased to about half of the control value after 40 min immersion in cold water.
　4. So, in the actual diving in severe cold water, the numbness and decreasement in agility of the hand seemed to become the factor limiting the working time.
　5. From these results, it was concluded that 1) the dry suit was effective in thermal insulation and 2) the development of diving gloves with high thermal insulation and mobility was very important for diving work in severe cold water.

DESCENTE SPORTS SCIENCE Vol.7/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE