ligot, I would check your boats capacity 79 gallons does not sound right for a cat. Are you sure there are not 2-79 gallon tanks. We are a 40' mono which carries 120 gallons and we can last 5 days easy. We also have 2- 5 gallon collapsible showers (Walmart). The are great and left in the sun, you get a pretty warm shower. We can get 2 showers out of each. Fajardo is the closest place to get water.