Hempstead Harbor is a V-shaped saltwater bay on the north shore of Long Island, New York, bordering the western portion of Long Island Sound. It runs approximately 5 miles long and encompasses 14 miles of shoreline, providing a significant area for exploration by kayak, canoe, or paddleboard. The harbor is characterized by its mix of developed shoreline and preserved natural areas, with parks and nature preserves lining its edges. The water body is categorized into lower, middle, and outer harbor areas, with the outer harbor reaching depths of up to 10 meters and featuring a rocky bottom.

Several public access points are available for paddlers. A primary launch is the Garvies Point Boat Ramp in Glen Cove, which is noted as an excellent, no-fee kayak launch. The Town Dock, which also serves as the Harbor Patrol Headquarters, offers a boat ramp with daily and annual permit fees for residents and non-residents. Bar Beach Park features a boat launching ramp described as very easy for kayak access. Other potential launch or stopover points include Harry Tappen Beach, Sea Cliff Beach Park, and Pryibil Beach in Glen Cove. A rental operation inside Safe Harbor Marina on Glen Cove Creek provides kayak and paddleboard rentals with a dock launch into the harbor.

Paddlers should be aware this is an active harbor supporting both commercial and recreational boating. The presence of marinas, yacht clubs, and fuel transport indicates significant boat traffic, necessitating caution, especially when crossing channels. The harbor experiences tidal flushing, and paddlers must account for tidal currents common to Long Island Sound. The fetch across the harbor can create choppy conditions, particularly when winds oppose the tide. The middle harbor area is noted for having turbid water.

The area holds ecological significance, designated as an Important Bird Area and a Significant Coastal Fish and Wildlife Habitat. Wildlife sightings can include osprey, herons, egrets, waterfowl, diamondback terrapins, and on rare occasions, pods of dolphins. Historical sand and gravel mining has impacted the area, but ongoing restoration efforts aim to improve water quality, remove invasive species, and revive wetlands. While shellfish populations exist, commercial shellfishing is prohibited in the harbor. Lifeguards are typically on duty at beach parks like Hempstead Harbor Beach during the summer season.