Denis is the founder of the US Open Water Swimming Association. USOWSA's mission is to support the development of safe open water swimming practices and events throughout the country while working to protect and preserve the waters of the world. Open water achievements include winning the 24 mile Tampa Bay Marathon swim, being the first international swimmer to cross Samana Bay in the Dominican Republic (16k)and a 2nd male finish of the 2007 41k Lake George Open Water Swim.