A study performed at the University of Florida showed slightly more calories are burned in cold water exercise than in warm. In the study, men who exercised for 45 minutes in 68 degree water burned an average of 517 calories. The men who exercised in 91.4 degree water burned 505 calories, on average.
from very cold to very warm is just twelve extra calories
But even in that case, you’d only burn a few additional calories at best, Cypess said. In studies where he’s put participants in cold rooms for entire days, they burned off an additional 150 to 200 calories. Again, that’s a full day of cold — not an hour’s worth of outdoor activity.
https://www.vox.com/2017/12/23/16774320/exercise-in-cold-bur...
vast majority of energy is expended by exhalation of carbon dioxide, not warming
Yes, a person in 60° water is losing heat energy more quickly than someone in 60° air. This is because water is much more efficient at transferring this energy - something like 24x IIRC.
Determining an equivalent air temperature requires knowing a bunch of additional factors (e.g. humidity). I don’t know of a rule of thumb you could apply other than saying the equivalent air temperature of water below one’s body temperature would be much colder, and the inverse would be true for water temperatures above one’s body temperature.