“A boat is a hole in the water into which you pour money” is a popular saying that has been printed on gift items, such as T-shirts and posters. “A yacht, they say, is a hole in the water surrounded by wood into which money is poured” has been cited in print since at least 1961 and is of unknown authorship.
 
Other sayings about boat ownership include “The two happiest days of a man’s life—the day he bought the boat and the day he sold the boat” and “BOAT: Break Out Another Thousand (dollars).”
     
 
Sports Illustrated
September 25, 1961
12 Days Before The Mast
What can you say about the sea? Only that it is big, said Chekhov. But a landlubber who sailed in the Transpacific race found a lot to say—most of it bad
Gilbert Rogin
(...)
Wally was in oil and obviously quite wealthy: a yacht, they say, is a hole in the water surrounded by wood into which money is poured.
   
Google Books
The Grantland Rice Award Prize Sports Stories;
The twenty-five most memorable true stories written since the death of Grantland Rice
Edited by Robert Smith
Garden City, NY: Doubleday
1962
Pg. 307:
Wally was in oil and obviously quite wealthy: a yacht, they say, is a hole in the water surrounded by wood into which money is poured.
       
12 June 1962, The Evening Standard, “Hollywood Today” by Erskine Johnson, pg. 2, col. 3:
Cleopatra’s barge, 220 feet long, was enough to remind us of that slick definition of a boat:
 
“A hole in the water surrounded by wood into which you pour money.”
 
1 July 1962, Independent-Press Telegram (Long Beach, CA), “‘Boatese’—Tongue of The Sea-Farer,” pg. W2, col. 2:
There is one more. It’s the definition to cover the total craft given by Robert Elms, commander of the Long Beach unit, United States Power Squadron. As Bob puts it:
 
“A boat is a hole in the water surrounded by wood in which to pour money.”
 
1 January 1963, Raleigh Register (Beckley, WV), “Hollywood Gems Of Wit, Wisdom” by Erskine Johnson, pg. 4, col. 2: 
CHARLTON HESTON talked himself out of buying a boat with this explanation: “A boat is a hole in the water surrounded by wood into which you pour money.”
 
21 September 1964, Evening World-Herald (Omaha, NE), pg. 6, col. 5:
Definition of a Boat
Mark Beltratre in Detroit Free Press
“A boat is a hole in the water into which you pour money.”
     
11 May 1965, Evening World-Herald (Omaha, NE), pg. 15, col. 3:
Definition
Today’s dandy definition (from Don Gordon of Westport, Conn.): A yacht is a hole in the water lined with wood, into which you pour money.
 
Google Books
March 1968, Popular Mechanics, “My First Year in Boating And What It Taught Me” by Wallace Cloud, pg. 158, col. 1:
“Son,” he said, “always remember that a boat is a hole in the water that you have to keep pouring money into. And you’re lucky to have a berth here.”
   
Forbes.com
8/01/2012 @ 11:58AM
Professor Billionaire: The Stanford Academic Who Wrote Google Its First Check

By Ryan Mac
It’s dusk on a crisp January day at Stanford University, and David Cheriton is in his corner office waiting for his weekly research meeting to begin. The last slivers of sunlight filter through the windows, illuminating the pages of Superyacht Living & Style, a glossy magazine Cheriton is browsing through with only the mildest of interest.
 
“I once read that a boat is a hole in the water where you pour in a bunch of money,” says Cheriton.