Red Tide finally showed up in the ocean around my place again. Gonna be a smelly week (or few days, I'm hoping), so no walking on the beach or swimming in the water for a good while; even going outside would be a bit much when it gets warm out.
On another note, this could be an interesting feature Toady could implement for DF (for those island and beachside forts). Just imagine plenty of miasma clouds coming from the waters every other season (with (patches of) water turning red/brown from the algae, plankton, and dead fish) for a short while as (rotten) fish wash up on shore. The water and/or miasma could have a chance of giving basic sicknesses to dwarves (and any other creature; based on experience of getting a sore throat or a cold from too much Red Tide being breathed in (or by swimming in it) before).
Other Red Tide Facts:
Red Tide Fact SheetLike I said, it could be an interesting feature to include. Fun as hell when it strikes your town. Good source of ‼FUN‼ (miasma being the straw that breaks the emotional camel's back) for fortresses when it's unexpected; especially if fish is your main source of food (poisonous shellfish), or you build your fort on top of the water. Irritated lungs are also a fun hindrance for fort dwellers and adventurers as well. Just imagine widespread sore throat sicknesses and such for a short while in a fort out of nowhere. Your hospitals will be having some fun diagnosing and helping out the infected.