I know this is an old article, but wondering if there have been these types of problems associated with the seaweed SXM has been seeing lately. Carol, I apologize if I'm not supposed to link this. You can delete it if I'm violating any copyright rules by posting the link. Again, please note this article is from 2011.

http://www.todaysxm.com/2011/08/10/seaweed-emits-poisonous-hydrogen-sulfide-beach-closures-possible/

The majority of the current seaweed is smaller and a much darker type than the picture. As it arrives it is well mixed with the waves/surf.
Some is a lighter color, float atop the water, and can be seen from quite a distance.
Neither has an odor.