The area in and around San Francisco and the larger Bay Area is, quite obviously, full of places to boat, sail and enjoy the water. While the water in the ocean itself may be a little too cold for the liking of many would-be swimmers, there are also plenty of rivers, lakes, and the like where one can take a dip in the warmer months.
There is a growing awareness of what could rightly be called a silent killer on the water. This phenomenon, called electric shock drowning, happens when a someone in the water encounters an electric current. Water conducts electricity fairly well, but it does not change in looks or anything else when it is doing so. To a swimmer, water carrying current looks like ordinary water.
This current may not on its own be of enough force to electrocute a swimmer. However, aside from the surprise of being shocked, the current can cause the swimmer's muscles to seize up and cause other symptoms of electrical shock. The end result is the swimmer, who may be healthy and a good swimmer, winds up drowning.
Obviously, though, the current in the water has to come from somewhere. In theory, anything with an electric current can diffuse that current in to nearby water, but it is often faulty boating equipment or a defective charger at a marina that leads to a potentially deadly situation.
While it is therefore best for swimmers not to swim around boats and electrical boating equipment, that does not mean that it is a swimmer's fault if they suffer electric shock drowning.
Boat owners and owners and operators of marinas in the area have an obligation to make sure their equipment is in good order and not prone to causing seepage of current. If they fail in this obligation, they can be held accountable under California premises liability law. Other legal theories may be helpful to them as well.