Hi Ryan
goose bumps result from the tiny pili muscles attached to each hair, that when contracted the hair raises vertically from the skin and causes a little bump. In our hairy/furry mammalian cousins, this "raises the hackles" both for thermoinsulation and fear/dominance situations.
Fur seals have fur but their pili muscles are gone, because hair-raising doesn't do any good in the water, it doesn't help stay warm, that's why they have blubber, the fur keeps them warm ashore and on ice packs.
True seals have lost both the pili muscles and the fur coat.
Humans lost most of the fur coat, the remainder is hydrodynamic, filling the voids of the body during diving. Our pili muscles still work, but add very little warmth when activated.
Water transfers heat much faster than air, depending on the speed of the currents. Wet skin obviously cools lots faster in fast wind than when in still water.
Shivering is partly affected by metabolism, so energy level is probably significant, not sure which one, probably blood sugar/glycogen. I haven't figured out shivering, obviously a self-warming thermostat system, but how does it fit in water? Do fish or dolphins shiver? Do other animals shiver?
When I swam up in Crescent City beach Calif. in 51 degrees pacific water, I really couldn't think about anything except getting in and getting out asap.
I'd wanted to try experimenting, but just couldn't get relaxed enough. Wait til warm waters.
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