“Boatgating” (boat + tailgating) is when a tailgate picnic is held from a boat instead of a car, van, or pickup truck. The tradition appears to have started at the University of Washington and is also practiced at the University of Tennessee.
 
The New York (NY) Times wrote about Washington’s tradition on October 13, 2011:
 
“Once docked or anchored, they tailgate with a twist, a practice the locals have alternately called boatgating, sailgating and sterngating.”
 
The word “boatgating” has been cited in print since at least 1996; “sailgating” has been cited in print since at least 1991 and “sterngating” has been cited in print since 1994. Boatgating differs from tailgating in that boatgating usually has less grilling of foods (to prevent boat fires).
         
 
7 September 1996, Los Angeles (CA) Times, “Tennessee Pumps Up Volume, Attendance” by Allan Malamud, Sports, pg. C7:
The only other place in college football where boatgating is as popular as tailgating is at the University of Washington’s Husky Stadium, on the shores of Lake Washington in Seattle.
 
Google Books
July-August 2003, Boating Life, pg. 12, col. 1:
If you do indeed bleed purple, you might be able to moor alongside this stadium on Lake Washington in Seattle. Otherwise, you’ll need a season permit to nab a coveted slot for prime Husky boatgating.
 
YouTube
Inside Tailgating - Boatgating With the Vol Navy - Knoxville, TN
InsideTailgating
Uploaded on Oct 3, 2010
The Inside Tailgating video crew literally hitched rides in the back of fan’s trucks over to the Neyland Stadium in Knoxville, TN to investigate the wild tailgating scene. Perched above the river, the stadium was surrounded by a sea of orange tents and trailers coupled with smoke from grills as traveling University of Florida Gator fans duked-out spots next to University of Tennessee Volunteers alumni. Our favorite part? Boatgating with the Vol Navy crew on the river.
   
YouTube
So, what is boatgating?
Vince Holton
Uploaded on Dec 8, 2010
If you travel to the USA, you may have heard of tailgating. That’s when people have a party out of the back of their truck or car before a football, basketball, baseball or pretty much any sporting event. But boatgating? What’s that all about?
     
New York (NY) Times
Tailgating Crowd’s Unlikely Roar: Ahoy!
By GREG BISHOP
Published: October 13, 2011
SEATTLE — The University of Washington’s football stadium loomed ahead, beyond the traffic, as the Miles family steered toward its usual parking spot one Saturday last month. For 50 years, the family members have arrived at Huskies home games through this entrance the same way: grill gassed, coolers stocked with microbrews, clad entirely in purple.
 
Their routine would seem like a typical tailgate, if only there were cars.
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Once docked or anchored, they tailgate with a twist, a practice the locals have alternately called boatgating, sailgating and sterngating.
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Husky Stadium opened in 1920, and soon after, the boat tradition started, with fans stashing vessels in tall grass not 200 yards from the end zone. Docks were built around 1960, according to Dave Torrell, the curator of the university’s hall of fame, and early transportation from anchored boats often came from members of the rowing teams in exchange for tips.
     
PRWeb
One of the Most Unique Ways to Tailgate Revealed: Boatgating
Discover Boating names best stadiums for the latest trend in on-water tailgating.
Chicago, IL (PRWEB) August 23, 2012
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Boatgating, also dubbed sailgating, stern-gating or transom-gating, has become a unique way for boaters and sports fans to experience the tradition of tailgating with an extra element of fun. Game day starts and ends with a relaxing cruise on the water, much more enjoyable than sitting in pre- or post-game traffic. For those with boats furnished with access to a grill, refrigerator and ample seating area, boatgating becomes even more convenient. No lugging of grills, chairs or other cooking gear when it’s all on board.
 
Discover Boating’s picks for best boatgating stadiums are:
 
Husky Stadium (Seattle, WA)
University of Washington football fans have the right idea – arrive by boat, moor in Lake Washington, and pick up the shuttle boat service to Husky Stadium. The game day views of the Cascades and scenic Lake Washington from this locale are tough to beat. Unfortunately, for the 2012 season boatgating is on hiatus as Husky Stadium undergoes renovations with the team playing home games at CenturyLink Field in downtown Seattle.
More information (for the 2013 season): GoHuskies.com/transportation
 
Neyland Stadium (Knoxville, TN)
The Vol Navy, as this infamous group of football and boating aficionados are known, arrive by boat to cheer on the University of Tennessee Volunteers during home football games. On the banks of the Tennessee River, Volunteer Landing is a three-mile riverwalk in downtown Knoxville that includes a visitor center, full-service marina and restaurants. For home football games, expect plenty of boats tied up and grills fired up amidst a sea of orange and white.
More information: TheMarinas.net or 865-633-5004