Final answer:
The disaster that befalls the boat is a storm, as implied by Dr. Watson and evidenced by descriptions of severe weather conditions, the ship's failure to arrive, and sightings of wreckage.
Step-by-step explanation:
The type of disaster that strikes the boat from which the note in the bottle originates is a storm. Evidence such as the description of a long, loud swishing and a gleaming trail of phosphorescence like a blue flame on the water, the ship not arriving at its destination, and the sighting of wreckage with the initials L.S., all support the conclusion that the ship encountered a severe storm which resulted in its destruction.
This is the same explanation implied by Dr. Watson, suggesting that the reasonable cause of the ship’s demise was the storm itself.
The type of disaster that struck the boat from which the note in the bottle originates is a storm. The storm destroyed the ship, causing it to sink and leaving only the note in the bottle behind.