Barnes Sound is a large coastal sound located west of the northern portion of Key Largo, Florida, and east of the mainland. It is part of the interconnected waters that include Card Sound and Blackwater Sound, providing access to eastern Florida Bay. The sound is characterized by its open, exposed waters, which can develop a significant fetch. On easterly or southeasterly winds, these waters can generate waves of three to four feet, and up to six feet in Florida Bay proper, making conditions challenging for paddlers and necessitating proper equipment like a sprayskirt. Motorboat and jetski traffic is a noted hazard, particularly in channels and near bridges like the Card Sound Bridge. Paddlers should be prepared for crossing active boat channels.

Key launch points for paddlers include the Barnes Sound West Ramp at coordinates 25.29, -80.3754, which offers a boat ramp. Another nearby access is the Card Sound East Paddle Launch at 25.2849, -80.3615. Florida Bay Outfitters, located at the north end of Key Largo, is a popular and well-equipped launch point providing rentals and retail supplies, though parking is limited. Paddlers are cautioned not to park in the adjacent Caribbean Club lot. These launches provide entry points for exploring the sound and for longer trips, such as the nine-mile paddle out to the Nest Keys in Florida Bay via routes through "The Boggies" or Dusenbury Creek.

The area is part of the Florida Circumnavigational Saltwater Paddling Trail. The sound's waters are protected from some winds, making it a viable option when conditions are rougher elsewhere. The shoreline is framed by Australian Pines, though these are an invasive species. Wildlife includes American crocodiles, which inhabit nearby areas like Joe Bay. Given the exposed nature of the sound and adjacent Florida Bay, careful attention to wind forecasts, wave conditions, and tide stages is essential for safe trip planning.