Is the sea level rising, or is the continent sinking?
Level recorders installed at shore can't answer that question. However, satellites can recognize continental shift. That's why NASA launched its Ocean Surface Topography Mission (OSTM) using the satellites Topex/Poseidon, Jason-1, -2 and later -3 to solve the mystery. Jason-2 sent us topographical radar images, and its successor Jason-3 has additional tools on board -- a radiometer and a laser.