If you want the definitive answer read "A Speck on the Sea" by William Longyard. It is a compendium of every crazy voyage in every kind of small vessel. He describes dozens. There is a review with some citations here:
A SPECK ON THE SEA: EPIC VOYAGES OF THE MOST IMPROBABLE VESSELS | Sea Classics | Find Articles at BNET
The description of what Paul Boynton did is of special interest. It doesn't get much smaller than his "vessel".
Dick Pluta
AEGEA