It was a beautiful day on the water in Tampa, eight miles from the Republican National Convention. Hurricane Isaac was gone. The Hula Bay Club was the scene of a party honoring the Congressional Boating Caucus.

"Florida is a perfect state for us," said vendor Jeff Scheib. "The boating industry in Florida is second to none. And we're very much focusing on Florida as a go-to market for ourselves." 

Scheib was manning a display for Gevo, which makes renewable isobutanol. It can be dropped as a chemical solvent into paints. And Schieb says it has a lot of potential in the marine industry as an alternative fuel.

"There's a real market poll and a real market interest for next-generation fuels," he said. 

The watchdog group Public Citizen says these parties are a way of lobbying at the conventions by inviting delegates and showing them a good time. Lauren Dunn, spokeswoman for the National Marine Manufacturers Association, says Florida's marine industry had more than $1 billion in retail sales in 2010 and provided more than 30,000 jobs. She wants the delegates to know that.

"We have a couple of delegates and a couple of members of Congress that have stopped by," she said. "I believe we've had some folks from Georgia and Texas and North Carolina come so far. We're hoping for more as the day progresses as well. But we're thrilled to welcome anybody into the event who is interested in learning more about the boating industry and our impact on the U.S. economy."

Public Citizen says this year, each party has been given a public grant of more than $18 million for its convention. But private sources are expected to add another $37 million for the Democratic event and another $55 million for the Republican one. The group said in a statement that conventions "provide a golden opportunity for lobbyists to extend their lobbying activity off Capitol Hill."