New support for the communications value of a message consigned to the ocean in a bottle has been demonstrated by the experience of a Chesapeake, Va. boy who reports that the container he had dropped into the Atlantic Ocean in 1981 has turned up in Spain.

William Old Jr., now 13, tossed a vermouth bottle into the ocean on Aug. 11, 1981, in an offhand gesture aimed a breaking the boredom of a slow day of fishing about 30 miles off Cape Hatteras.

Old included his name and address on the note placed in the bottle, but as the days and weeks and months passed and the ocean rolled on as before, he gradually forgot about it.

Then a letter arrived recently from a lawyer in Spain, Jose F. Carreira, who wrote :"I am glad to tell you that your notice in a bottle landed safely just in the N.W. of Spain on a beach where I own a summer house."

The bottle apparently had been carried by the Gulf Stream on its course up the coast of the United States across the North Atlantic and down the coast of Europe.

"It's not unusual for something dumped in the Gulf Stream to end up on the coast of England, Spain, or even the west coast of Africa," said Dr. Harris Stewart, an expert in marine studies.