Here are a few links that may provide insightful information. Have been closely watching the sargassum issue since finding alot of it on beaches during our 2015 trips. Not good. Look at the density map found on link nr 2.

http://www.sciencemag.org/news/2018/06/mysterious-masses-seaweed-assault-caribbean-islands

http://optics.marine.usf.edu/projects/SaWS.html#2018.mean.400.png

https://www.riviera-maya-news.com/city-workers-removing-90-tons-of-seaweed-per-day/2018.html