ERA5 - Land, values on coasts

Question, please:  Do values for coastal grid cells in ERA5-land incorporate zero values over water, or are they means only over the land portion of the grid cell?  My guess based on the following map of soil moisture is that ocean is included in means with a value of zero, but I would like to be certain.  I have the same question in relation to other parameters - precipitation etc.  Thank you.

Illustration:  Soil moisture in  0.1o grid cells along the coast of northeastern South America is much lower than adjacent cells that are mostly or entirely land.  The following map is centered on Suriname with national boundaries in pink.  Ocean-only cells are grey.  Mapped values show long-term mean soil moisture for layer 1, averaged for each cell across twelve months.