Answer:
On a sailing ship, on the ocean.
This is a line from the Samuel Taylor Coleridge poem "The Rime of the Ancient Mariner". The main character laments the irony his dehydration, as a thirst has plagued the ship and her crew for quite some time despite the fact that they're surrounded by a seemingly endless expanse of water. The salinity of seawater and the limits of the human kidney are the reason why one can only become more dehydrated by drinking seawater.