They carried as much water as they could, in barrels and casks. When it rained hard, they caught rain water. There are many accounts of ships that ran out of water, or had to cut back to very small amounts, for days or weeks, until they reached land where water was available, or it rained hard enough to catch water.

Historically, old sailors relied on a combination of strategic planning and environmental collection to survive months at sea. The most common method was the use of wooden casks or barrels filled with fresh water from springs or rivers before departure; however, this water would often turn stagnant or grow algae within weeks. To supplement these supplies, sailors became experts at rainwater harvesting, using large canvas sails or specialized wooden troughs to catch runoff during storms and funnel it into storage. In the 18th and 19th centuries, some advanced ships began carrying early distillation units—essentially copper stills that used heat from the ship's galley stove to boil seawater and collect the condensed steam as fresh water, though this was fuel-intensive. Interestingly, many sailors also relied on "liquid substitutes" like beer, wine, or grog (watered-down rum), as the alcohol content helped kill certain bacteria and made the foul-tasting, older water more palatable during long transoceanic voyages.

Historically, old sailors relied on a combination of strategic planning and natural collection to survive months at sea. The most basic method involved filling heavy wooden casks at known freshwater springs or rivers during land stops before departure. However, as these supplies frequently became stagnant, slimy, or infested with algae over time, sailors became expert at "harvesting the sky." Large canvas sails or specialized "water cloths" were rigged during rainstorms to funnel rainwater into barrels. On some advanced 18th and 19th-century ships, small distillation units were introduced, though they were fuel-intensive and often produced a metallic-tasting water. To mask the foul taste and preserve the water's drinkability, sailors often mixed it with spirits like rum to create "grog" or with vinegar and molasses. By 2026, historians note that the search for fresh water was the primary driver for maritime exploration, as ships were often forced to risk uncharted coastal landings simply to avoid the deadly effects of dehydration and contaminated barrels.