Actually, the proper term is harmful algal blooms (HABs). They make seafood temporarily inedible, and probably aren’t so good to play in for humans, either. But, it didn’t really stop anyone from splashing around.
HABs happen every year, but not too often. They only last a day or so, and at night, they’re actually kind of pretty, as they glow blue.
Other than the harmful part, the only other downside is the smell—once all that phytoplankton (what a bloom is made of) washes up on shore, whew! What a stink!
…I’m not really doing a very good job selling Yuigahama Beach as a destination, am I? Well, I assure you that the tide, as well as the smell, don’t last very long—all of last year, I only saw it happen once, and the whole thing was over in about 24 hours. And, really, it was quite neat.