Alviso Slough is a tidal saltwater channel extending approximately four miles from the community of Alviso to the open waters of the south San Francisco Bay. The primary and only identified launch point for paddlers is Alviso Marina County Park, located at Mill Street in Alviso. This facility offers two concrete boat launch ramps and two floating docks, one of which is a low-freeboard dock well-suited for kayaks and stand-up paddleboards. Parking is free with no time limits, and the park is open from 8:00 a.m. to sunset, with automatic gates that close at dark. Tidal influence is the dominant hydrological feature, with a typical range of 9 to 10 feet and currents running approximately 1.5 mph. Paddlers must plan trips around these tides; a common strategy is to launch an hour before low tide to get a current boost both outbound and inbound on a return trip. The slough is bounded by levees, providing a mostly enclosed, calm-water experience until reaching the bay. Powerboat traffic increases on higher tides, but is otherwise minimal. Navigating upstream from the marina leads under several bridges, with navigable water typically ending around the Highway 237 bridge about a mile away, except during very high tides over 8 feet when more reed-lined channels may be explored. Paddling downstream leads toward San Francisco Bay, which is a more exposed, open-water environment. The slough passes through the salt marshes of the Don Edwards San Francisco Bay National Wildlife Refuge, offering opportunities to see shorebirds and occasional harbor seals, with wildlife viewing often better at lower tides. The waterway is a good first paddle for beginners due to its generally calm conditions, though venturing into the bay requires experience appropriate for open, tidal salt water. The surrounding landscape is characterized by salt ponds and marshes, with historical remnants like old salt hardpan visible in some areas.