Jan de Null operates the 2017 built Adhemar De Saint-Venant. The ship is designed to lay rock on the ocean floor.

The vessels will be able to install rock at depths up to about 600 m by means of a flexible fall pipe to allow for accurate rock installation around structures such as offshore wind turbine foundations and Oil & Gas platforms. The ships Spec Sheet (PDF) give a good view of the vessel

the ship sailed from Saint John, and was spotted off the Coast of Virginia, likely building the bases for the Offshore wind farm which was installed by Vole au vent out of Halifax.

The ship is named after Adhémar Jean Claude Barré de Saint-Venant who developed the unsteady open channel flow shallow water equations, known as the Saint-Venant equations, that are a fundamental set of equations used in modern hydraulic engineering

Update:
Sailed at 1400 under fog.