I would love to take that trip. I went to a turtle release there last week. I have been thinking about the issues of water, sun, etc. Especially water.
In summer, I think the hiking would be at night. (Oddly this would allow for bare feet, no sunscreen, etc.) Days would be spent under a tarp and a wet sheet.
I am drawn toward the solar still solution because it collects during the day. And digging before dawn should be doable.
After a bit of reading, I can't come to a conclusion on the practicality of a solar still. Accounts of 1 liter per day are unacceptable, but who knows what size hole and tarp? This digging could get old after the first night. Some commercial varieties exist for use on life rafts. These are expensive ($400) and even though inflatable the weight and bulk are too great. Even then the capacity is 1.5 liters/day. Well short of the 4 liters I would like.
I have been trying to wrap my head around a lighter MYOG solar still solution using external support, like CF poles. Any thoughts?