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.