All of those variables to me appear like they would be similar on land. Currents move but so does wind, and I don’t think their are any currents in the ocean that can rival hurricane force winds that trees can contend with.
Sunlight also changes quite a lot on land depending on the season or weather.
Just can’t see why underwater trees aren’t a thing.






















Well, ya but I don’t think it would be 100% identical to trees. Lignin didn’t really even exist for millions of years before trees evolved to fight gravity on land. But underwater you wouldn’t need a strong trunk like that since they would weigh so much less and can evolve buoyancy structures or something like other plants do. Or even short and stout, just massive.