Hard to buy water 786 miles off the coast of paradise. Boat boys don't come out that far.
I disagree on the size issue; don't have one yet but spec'd out one - Katadyn 80E because:
a) I need a modular unit.
b) I want to run it off DC, not the motor (I like quiet, and have solar).
c) I only need 8 amps to make roughly 4 gallons - I can make that off solar alone and never touch my batteries (don't bring out your calculators solarstik fans, 2 X100 watt panels will make 8 amps for at least a hour per day.
If I need more than 4 gals a day to drink, cook, wash with, I'll let it run for more than one hour, if not I'll play with my laptop a little more