For health reasons, your sub should always be free to drink as much water as she needs.
Go bona itekanelo e e gaisang, metsi a go nwa a a phepa a rurufetse a tshwanetse go nna teng go dikolobe tsotlhe ka metlha, gore di nwe metsi ka bontsi jo di bo batlang, ka nako e di batlang.