In fresh water what makes lightening so dangerous to a swimmer is that most of the current travels on the surface of the water, so rather then getting a 1/r**2$1/r^2$ falloff in current density, you see a 1/r$1/r$ falloff. Obviously eventually it will be conducted down into the mass of the water, but this takes a many meters. In salt water, this should happen much quicker. I'm not sure how the conductivity of the inside of your body compares to seawater. Even if it is less, some current would still flow through you.
For normal dry skin, it takes considerable voltage to penetrate the skin (maybe a hundred volts), wet your skin with saltwater and you'lyou'll conduct electricity quite well! As a teenager playing with cheistrychemistry and water, that happened to me once, 12volts12 volts AC and ionic solutions made for a pretty nasty shock. Normally 12volts12 volts won't penetrate the skin, so I was unrealistically confident!
I have a spark generator that makes roughly 20KV sparks (from a capacitor), discharge it into water, and you see surface sparks spread from the point of entry in all directions.
