Why does a 104°F pool/tub feel boiling hot, whereas a pot/cup of water at the same temperature does not feel hot at all.
(Normally a pot/cup of water won't be hot enough to cause one to immediately remove ones finger from the water till it's around 165-175°F).
Probably same conductivity, specific heat, BTU's (since the amount of BTU's needed to raise 1°F is proportion to volume of water. Meaning, 1 BTU is needed per pound, so no matter what the volume is it will contain the same BTU's per pound).
Perhaps there's much more "heat" (BTU's/Joules) available in a tub/pool to "refill" the spot which transferred into ones body (perhaps through conductivity) not allowing the area of water touched by ones body in the tub/pool to cool off fast enough.
Another possible factor might be that perhaps there's an increase in convection; not sure if the higher the volume of water, the higher the convection.