Coconut water is one of the two products of separating a coconut at a kitchen (10 second STR timer; 1 coconut yields 1 coconut water and 1 coconut meat).
With level 2 in the Desiccation skill, 25 coconut water can be converted into 3 salt by boiling it in a kettle. The process is very similar to that for producing potash, except that no additional water is required.