The River Arun in West Sussex is a significant tidal river, navigable by paddlers from its mouth at Littlehampton inland to Pallingham Quay, a distance of over 25 miles. The character of the river changes dramatically along its length, offering varied experiences. The upper, non-tidal section around Pulborough and Stopham Bridge is slow, wide, and calm, winding through water meadows and tree-lined channels backed by the South Downs. This area is suitable for beginners, families, and self-led hire, with a peaceful, scenic vibe rich in wildlife like kingfishers and herons. In contrast, the tidal section from Littlehampton through Arundel is a powerful, fast-flowing environment with currents between 4-6 knots. This area is exposed to wind, features turbulent water around harbour bridge supports, and has significant boat traffic, making it suitable only for capable, experienced paddlers with proper safety equipment.

Critical trip planning revolves around the tide, which affects the river far inland. A common and recommended day trip is the one-way journey from Arundel to Pulborough, a distance of approximately 13 miles taking 3-5 hours, which requires careful timing with the tidal flow. Another popular circular route utilizes the tide for an upstream and downstream journey between the Black Rabbit pub in Arundel and Amberley, a round trip of about 9 miles. Paddlers are strongly advised to consult detailed tide tables, noting that high tide at inland points like Amberley occurs roughly two hours after high tide at Littlehampton. Launching and landing points are tide-dependent, with steps at sites like the Black Rabbit becoming more or less exposed.

Key access points include purpose-built facilities at Littlehampton (Surrey Street car park, BN17 5AW), the Black Rabbit pub steps in Arundel (BN18 9PB), various points around Pulborough and Stopham Bridge, and Pallingham Quay upstream. Commercial hire and launch services are available at Pulborough and Stopham Bridge. Hazards are concentrated in the lower, tidal reaches and include strong currents, turbulent overfalls, wind exposure, and boat traffic. The river mouth at Littlehampton can develop a surf zone and turbulent water on an outgoing tide. No paddling permits are required for the river itself, and the primary season for recreational paddling runs from March to October.