How long would you survive?

In My Humble Opinion
81

Drinking water is going to be the least of your problems on the Aucklands. Here’s a paper on climate. There rainfall isn’t extreme (between about 60 and 80 inches depending on locality) but it rains between 311-331 days per year, mostly in the form of light rain and drizzle. As the photo I linked to shows, there are small streams everywhere.

However, if you do need to transport or store water, there are a few possibilities. There seem to be only about three or four species of tree found in the coastal forest in the Auckland. However, one of them is Pseudopanax simplex. The bark of a related species, P. arboreus, was used by the Maori to make small water vessels, and the gum was used to prevent leakage. Given time, you might make sturdier vessels by carving bowls out of rata.

Incidentally, the Southern rata has additional uses besides firewood. The bark was used as a medicinal to treat wounds, and the roots were made into fishhooks.

82

There’s also pig bladders for carrying water. And kelp pneumatocysts can also be dried out and used as water vessels.

83

I live in England. I’ll be OK.

84

People in England die of exposure from time to time when its cold and wet and they are caught outside, usually hillwalking. IIRC this has reduced significantly since the major improvements in outdoor clothing (goretex and fleece, basically). That’s why I say this OP is so heavily dependent on exactly what you are wearing when you wash ashore.

85

Given meds, forever. But since that ain’t gonna happen I went with months.