The Boston Public Health Commission reports an explosion of blue-green algae in Jamaica Pond means the water's no longer fine for fishing or for dogs and kids to go in.
Also banned until the cyanobacteria bloom dissipates: Boating.
Based on initial visual inspection of the pond, it appears likely that Jamaica Pond is experiencing a harmful algae bloom. These blooms may produce toxins that can make people and pets sick. Park visitors are urged to avoid contact with the water and any areas of algae concentration, even on shore.
In the event that you, your child, or your dog comes in contact with the water or an algae bloom, rinse off immediately.