Does lightning kill creatures in the oceans?

Answer 1

Only those very close to the point of the strike. Lots of little critters might die 'cause there are so many of them in the water, but probably not too many fish or larger creatures are killed. Recall that the ocean is salt water, and salt water is a pretty good conductor of electricity. The charge will spread out and dissipate quickly and within a pretty small area because the salt water distributes the charge so efficiently. Fatal shocks are probably only suffered by critters within a few dozen meters of the spot the bolt strikes. The physics of the issue is that charge density of the current will drop like a rock as something like the inverse cube of the distance from the point of the strike (except near the surface, where it might be between the inverse square and inverse cube), if that helps.

Answer 2

Lightning can kill creatures in the ocean if they are close to the surface when a strike occurs. However, because ocean water is a good conductor of electricity, lightning tends to disperse rapidly in all directions once it enters the water, minimizing the chances of a direct hit on a specific creature.