What is the definition of a "kayak"?

Over the years, there have been several major crossings of oceans by people using "kayaks". However, if we look at each of the actual boats used, these "kayaks" would look quite different from each other.

• 1928 - Franz Romer crossed the Atlantic using a modified 21.5-foot Klepper folding kayak mostly under sail.
• 1956 - Hannes Lindemann crossed the Atlantic using a 17-foot Klepper folding kayak under sail.
• 1987 - Ed Gillet paddled a Necky Tofino tandem sea kayak by himself from California to Hawaii.
• 2001 - Peter Bray crossed the North Atlantic ocean paddling a 27-foot custom built kayak with a cabin.
• 2007 - Andrew McAuley made a tragic, unsuccessful attempt to cross the Tasman Sea in a modified stock tandem Mirage kayak that was just under 21-feet long.
  
• 2007-08 - James Castrission and Justin Jones successfully paddled across the Tasman Sea in a custom built tandem just over 29-feet long with a sealed cabin behind the cockpits.
• 2010-11- Aleksander Doba crossed the Atlantic in a 23-foot custom-built kayak that was self-righting and had a sealed cabin.
  

Of these seven expeditions, only Ed Gillet used a totally stock sea kayak without modifications. Andrew McAuley's kayak had some modifications to increase volume so he could carry enough food and gear. Romer and Lindemann used stock folding kayaks that were only modified somewhat, but they mostly sailed their kayaks and only used paddles occasionally. Bray, Doba, and Castrission/Jones paddled, but had kayaks that included a sealed cabin for sleeping.

When McAuley and the team of Castrission/Jones were making their preparations to cross the Tasman Sea, the sea kayaking legend, Paul Caffyn, expressed his feeling that using a 29-foot kayak with a cabin was essentially "cheating". It wasn't really a "kayak" in his estimation.

How do you feel about this question? What is the definition of a "kayak" for the purposes of doing a major crossing for the record books? Does it matter? And what about all the new communication technology that is available to today's adventurer? We'll address that specific issue another time. For now, let's focus on the definition of a kayak. What do you think?

Sherri