system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why does 70° F water feel freezing, while 70° F air feels warm?

I was in the ocean today and it was approximately 69° F.  It felt absolutely freezing.  I always wondered why similarly hot/cold air temperatures feel warmer or more pleasant than water temperatures.
gpt
I had problems with understanding this for a long time, so here goes:

When things "feel cold" what you're feeling the heat leaving your body.  If something feel colder, it's because it's pulling heat away from your body faster.  This is why 50 F air feels chilly, but 50 F water feels WAY colder.  Although they are both the same temperature, the water conducts heat away from your body faster, which is what you feel.

70 F feels warm because it's conducting heat away from you slow enough that your body doesn't really care.  Water of the same temperature takes that heat faster, so it feels colder.