Guadalupe Slough is a tidal slough located in the South San Francisco Bay, within the Don Edwards San Francisco Bay National Wildlife Refuge. It is a saltwater feature directly connected to the bay, characterized by significant tidal influence with a range exceeding 11 feet, which can expose extensive mudflats during low tide. Paddlers must consult a current tide chart for Upper Guadalupe Slough before any trip, as navigating the slough at low tide is impractical and potentially hazardous due to these mudflats. The slough is bordered by managed ponds and levees, with public trail access along some levees. A primary access point for launching small craft like kayaks is from the Alviso Marina County Park area, which provides boat ramp facilities. The slough's waters are part of a major wildlife refuge, offering paddlers views of tidal marsh habitat and significant bird populations. Waterfowl hunting is permitted in adjacent ponds on specific days, primarily Wednesdays, Saturdays, and Sundays, which paddlers should be aware of for both safety and seasonal noise considerations. The overall paddling experience is defined by its open, marshy landscape and is heavily dependent on correct tidal timing. The slough is not recommended for power boating or for those unfamiliar with its channels due to the navigational challenges posed by the tides and mud.