Exo 15:23 And when they came to Marah, they could not drink of the waters of Marah, for they were bitter: therefore the name of it was called Marah.
Exo 15:24 And the people murmured against Moses, saying, What shall we drink? Exo 15:25 And he cried unto the LORD; and the LORD shewed him a tree, which when he had cast into the waters, the waters were made sweet: there he made for them a statute and an ordinance, and there he proved them,
I posted about complaints of the people in yestarday’s blog.
As you can see this continues at Marah.