0 a mark that shows the highest level that the sea or river reaches at a particular place --
1 the most successful point of something: --
The move to political integration has reached its high water mark.
The measure is a high water mark in education since 1944.
We may have to extend below high water mark a big slipway, or something of that sort.
The draftsman was so correct that he forgot the problem of flooding, which could stretch beyond the conventional high water mark.
I wish to make it clear that there is absolutely no intention of having a marine nature reserve above the high water mark.
It would provide the maximum area of water within the engineering constraints and would be broadly equivalent to mean high water mark.
Of course there is the possibility that some wreck might be involved in a storm and tossed above the high water mark.
It was not by any means the high water mark of our demands here for 40 or 50 years.
