So, I was looking for a drop-in replacement for swimming (~3-~4km per day, so ~60-90 minutes plus commute) that could be done:

• outside

• by myself

• in the winter (~-10°C)

• without needing access to any (locked down) facility

• or significant investment in equipment

• or additional time

• that isn't mind-numbingly boring

• and that would yield a similar metabolic effect.

"No choice" is shorthand for "I don't feel like plumbing the depths of all possible forms of exercise to come up with a suitable match under these constraints so I'll just pick running."

Genuinely interested in any alternatives that satisfy those criteria because I bet they'd be creative.

As for the ice, I bought a decent pair of trail shoes that seemed to work fine.