If you include a WAVx primative in any load case, then the weight primative "W" is actually "W+Buoyancy".

You can prove this by defining a submerged cantilever, with some small generic wave loading. Then make two runs:

1) In Run1, just define a single load case with "W", run the analysis and note the vertical reaction load.

2) In Run2, define a second load case with "Wav1", run the analysis and note the vertical reaction load for 'case 1 - W'.