Final answer:
The situation that would NOT be covered by the watercraft endorsement under the homeowners policy is when a friend rents their boat and runs it into a neighbor's dock.
Step-by-step explanation:
The situation that would NOT be covered by the watercraft endorsement under the homeowners policy is option 4) A friend rents their boat and runs it into a neighbor's dock. This is not covered because the watercraft endorsement typically only covers the boat while it is being used by the insured or by someone with the insured's permission. Renting the boat out to a friend and allowing them to use it would likely be considered outside of the policy's coverage.