During August & September 2022, San Francisco Bay experienced a Red Tide bloom that made headlines. Over the course of two months, the water, which is warmest around August and September, turned a dark mottled brown color, starting in select locations and eventually taking over the entire Bay Area. Visibility was reduced to zero in the water.

Some divers chose to stop getting in the water out of health concerns. From the hull cleaning perspective, the visibility was terrible, making the work slower and difficult.

However there was a huge benefit due to lack of sunlight: Very little seaweed or algae was growing in the darkness of the murky water, making certain boats much easier to clean. Any boat that would normally have a beard of kelp and algae on the propeller within 4 weeks, was now almost completely clean after 4 weeks. This benefited the longevity of bottom paint as well, as the harshest months of summertime when the bottom paint is usually taking a beating were made significantly less harsh thanks to the murky water.

The algae die-off produced a red powdery substance that affected a handful of boats, some worse than others. It seemed that the more smooth a paint surface, the more likely the red die-off residue would stick to the hull. This residue was not easy to scrub away, but otherwise it did not seem to leach copper out of the paint and turn green, as some other substances like herring roe can do.

red algae

Keywords: Red Tide bloom, San Francisco Bay, Red Tide die-off, algae bloom, algae die-off, murky water, visibility, hull cleaning, seaweed, algae, propeller, bottom paint, algae residue, red die-off residue smooth paint surface