Back Bay, also known as Upper Newport Bay, is a large salt marsh estuary and the largest remaining estuary in Southern California, located in Newport Beach, Orange County. The primary and best launch point for paddlers is North Star Beach, adjacent to the Newport Aquatic Center. This location offers free parking in a large sandy lot and free beach launching for kayaks, canoes, and stand-up paddleboards; rentals are also available at the Aquatic Center. Another launch option is from Lower Castaways Park, which provides free parking but no restrooms, and offers access to the lower bay and marina areas towards Balboa Island. Launching from spots along Back Bay Drive is only advisable at a fairly high tide. The estuary features extensive wetlands dotted with islands and sandbars, with numerous little rivulets snaking through the marsh. The main channel is deep enough for paddling, but moving out of the center leads to very shallow water, as shallow as eight inches in places just 30 feet from shore. Paddling guidelines, posted on buoys, instruct boaters to stay out of the upper part of the bay and to avoid paddling up the narrow side channels, which can become too tight to turn around in.

The afternoon onshore sea breeze is a significant factor, often blowing up the bay. A common strategy is to start a paddle in the late afternoon, heading northeast up the bay with the wind at your back, and returning around sunset when the wind typically dies down. Tidal currents are present but are generally considered less of a factor than the wind; however, timing a trip to paddle up the bay with an incoming tide and return with an outgoing tide can make the journey easier. The area is an ecological reserve home to many birds and several endangered species, offering excellent bird watching opportunities. Commonly observed wildlife includes coots, avocets, least terns, herons, egrets, and black skimmers. The Newport Bay Conservancy offers guided two-hour kayak tours with a naturalist on weekend mornings year-round, highlighting the history and ecology of the bay. The overall experience is a relaxing and family-friendly alternative to typical tourist destinations, with a scenic mix of wetlands, open water, and views of surrounding cliffs in some sections.