We were at a resort about 15 miles south of Cancun near Puerto Morelos last week. The seaweed made the beach unusable. The resorts were trying to deal with it, but multiple tractors couldn't keep up. It wasn't just a nuisance--it completely shut the beaches down and the stench was pretty bad where it was decomposing. My family was fine with the pools/swim up bars so it wasn't a vacation-ruiner.
One day we took a catamaran out to Isla Mujeres, and there were small parts of the beaches there that had no seaweed--but everyone in Mexico seemed crammed into these few clean areas, and it was wall to wall people. We found some tidal pools on the north end of the island and enjoyed just wading there and looking at the fish.
I asked one of the locals there, and he said the seaweed problem was constant and that there seemed to be no way of really fighting it. If you haven't seen how bad it can get down there, it is hard to explain. It is washed up on the beach as far as 10 feet and it is up to 2-3 feet thick. Just massive amounts. There is so much floating in the water right off the beach that all the water just turns to a slush of weed and brown--the local guy called it chocolate milk.
I'll be interested to see what you find.