Well the water was right at freezing point, that’s snow all around, the lake was most of the way up a mountain, and the ice was 1.2m (4 ft.) thick! These guys are on Lake Alta in the Remarkables, near Queenstown. Strangely enough, they seemed to want the hot tub to get into when they got out of the lake.

The tub took two hours to heat fully which we think is pretty good, given the operating conditions plus freezing SCUBA divers plunging into it (like ice blocks into whisky!). Normally it’s much quicker. Pretty much anywhere else is easier.