The Rock Water type is one who have a very strict standard of living, and gives themselves very little leeway. The non drinker who won't drink, those are will deny earthly pleasures, or those who set the must utmost, rigid standards upon themselves are all examples of Rock Water types.
They are very rigid in their view of the world, and while they won't try and force their beliefs on others, they are very unwilling to bend or change their ideas.
Often they fear they are unable to live up to their ideals.
For Empaths:
It is not unusual, as an empath, and someone who aspires to be the best they can be, to put very high standards on themselves and their behaviour.
What that can lead to is rigid standards and self-denial from the basic joys of life. Sometimes we make sacrifices to get to where we want to be (and sometimes we don't!) but there are some levels where we are denying ourselves things that we could have, but choose not to do because we believe they are not spiritual or something you should do, or worse, what others feel you shouldn't do.