“Governments are the only vessels that leak from the top” is a popular government saying referring to the leaking of information. A sailing vessel leaks water from the bottom.  On November 9, 1946, New York (NY) Times political reporter James Reston wrote: “Some of the reports were false and misleading, but since governments are the only vessels that leak from the top, a good deal of accurate information leaked out…”
 
Reston often repeated the saying. Other versions include “A government is the only vessel that leaks from the top” and “The ship of state is the only known vessel that leaks from the top.”
 
“The New York Times is the official leak of the State Department” was said by Canadian-American comedian and social satirist Mort Sahl in 1961.
 
 
Wikipedia: James Reston
James Barrett Reston (November 3, 1909–December 6, 1995), nicknamed “Scotty,” was an American journalist whose career spanned the mid 1930s to the early 1990s. He was associated for many years with the New York Times.
 
Answers.com: Quotes by James Reston
“A government is the only vessel that leaks from the top.”
“The ship of state is the only known vessel that leaks from the top.”
     
9 November 1946, New York (NY) Times, “Big 4’s Press System Seen As Approved by Reporters” by James Reston, pg. 4:
Leaks From Above
Reports of what went on at those meetings got out. Some of the reports were false and misleading, but since governments are the only vessels that leak from the top, a good deal of accurate information leaked out, including the central point that the Big Four agreed on practically nothing.
 
3 January 1951, New York (NY) Times, “No Easy Rule Seen for Giving Public Facts, Not Aiding Foe” by James Reston, pg. 16:
The most secret of all information—much in the field of atomic energy—has been passed on to a few legislators in the last few years. They have demonstrated that, while a government is the only known vessel that leaks from the top, this is not always so.
 
24 June 1956, New York (NY) Times, “The One Vessel That Leaks From the Top” by James Reston, pg. E8: 
Moral of the story: A government is the only known vessel that leaks from the top. Moral No. 2: Nobody is immune to the diseases of politics, not even the Crusaders.
   
Time magazine
Lid on Leaks
Monday, Jan. 25, 1982
(...)
As the old Washington saying goes, the ship of state is unique—it leaks from the top.
   
24 November 1983, New York (NY) Times, “His Own Petard” by William Safire, pg. A23:
“The Ship of State,” Walt Rostow is supposed to have said, “is the only vessel that leaks from the top.”
 
New York (NY) Times
On Language
Leaks
By BEN ZIMMER
Published: August 20, 2010
(...)
An early glimpse of how leak entered American political vocabulary comes in John C. Frémont’s 1887 memoirs, which recount a political event leading up to the Mexican-American War, when Secretary of State James Buchanan “discovered a leak in his department.” Buchanan needed to patch a leak from below, but by the end of World War II, leaks could just as likely come from above, in the form of information revealed to reporters by high-ranking officials who didn’t want to be identified. As James Reston wrote in a 1946 New York Times dispatch on postwar peace negotiations, “Governments are the only vessels that leak from the top.”