Have seen the same type of erosion in Playa del Carmen. Unintended consequences. What goes in front of the new establishments will undoubtable have some unfavorable consequences somewhere else on the beach.
Walkig by the other day I saw several of the beach fence posts that were already undermined.
Will TRY <img src="http://www.traveltalkonline.com/forums/images/graemlins/Yikes.gif" alt="" /> to overcome sand gravity tomorrow and take another walk tomorrow up that way.
Just as an update, this am a very little sargassum on the Club O beach section. Not remotely enough to cause any problem. Only limited sea grass floating in the surf.
Beautiful day on the beach.