(None on file)
This story became Chapter 3 of Majipoor Chronicles.
Majipoor is a really big planet, and its three continents are crowded into one hemisphere, leaving the other hemisphere to the Great Sea. No one has ever crossed it. But it is a time of great exploration (long before Valentine's era), and Captain Sinnabor Lavon decides he will be the one to do the impossible and circumnavigate Majipoor. All goes well until the fifth year out, when they encounter a mass of strange writhing seaweed which challenges their resolve.
(None on file)