My understanding is that drag is more about the "front-on" view of a craft than how long the craft is.
Since solar panels are very thin and aimed up, it feels like they add minimal cross-sectional area to the craft. Your assertion seems trivially incorrect to me?
Oceans can be extremely rough, but even mild waves make it inappropriate to approximate PV as thin.
The requisite area to power a ship is huge, something like 1.4km^2 (ballpark estimate for 20% cells, reasonable capacity factor guess, 60 MW consumption requirement). If a ship is about 30m wide, it's trailing about 45 km of PV. You're not even into 4 digits of cargo ships before the combined length is longer than the circumference of the planet.
> My understanding is that drag is more about the "front-on" view of a craft than how long the craft is.
Drag (fluid mechanics generally) is... ludicrously complicated. For the typical shapes of ships, I believe you are correct that the main factor is cross sectional area perpendicular to the direction of travel, but that’s not universally true. i think that for a floating raft of panels, it would be proportional to the panel area, similar to how for winged aicraft its the wing area and not the cross section perpendicular to direction of travel.
There's a pressure drag and skin friction drag. Friction drag is supposedly a majority component unless you sail a brick. But I don't have sources to prove that.
Ships drag across sticky goop, not fly through soup.