Not only that, but the chart is showing what amounts to the derivative of the change since 50 years ago where the variable in question varies by more than a meter twice a day due to tidal variation, and the waves (and wakes from boats) can be just as large.
The measurement itself has to represent some kind of filtered representation of the actual water level, which is varying constantly due to tides, currents, wind, wakes, the hydrodynamic effects of swimming fish, and even the ripples that result from a sea gull's poop landing in the water.
The trend in question is buried so far into the noise that it may well be just an artifact of measurement and processing.
Yep, signal to noise there is horrendous, isn’t it?
The proof is often found when you look at two photographs of the exact same spot taken 50 or 100 years apart and you see ZERO change in the water level.
100 miles up the coast, the tides are 50 FEET twice a day. And they get their panties in a wad over immeasurable fractions of an inch.