Some more commentary and info...
When you go to the beach, the most common warning system in the US is a series of different colored flags, that indicate different levels of danger in the surf
: "calm surf", "moderate surf", "high surf"/"heavy surf".https://www.breakersfwb.com/island-blog ... -meanings/http://www.emdonenilodge.com/the-comple ... ing-signs/
"Rough seas" is a weather warning used to describe rough conditions offshore
that would affect boaters and fishermen. You will see this if you go to youtube and search for "rough seas": there are no videos from the beach.
"Swollen seas" is a description that comes from the name given to those waves that have developed far offshore: "Swells". And if you look, you can find the swell forecast for a given day in the surf report: https://www.surfline.com/surf-report/we ... d6a7708b8b
A swollen sea will be one with higher swells
than normal/average, and this could be used to describe weather offshore or at the beach.
In Galveston, near where I'm from, "moderate swell" or "high surf" come in from time to time, but I don't recall inundation as bad as in those videos except during storm surges.