Tidal flows in the deeper water of the Solent can be stronger than in the approaches to Cowes Harbour and may even run in the opposite direction to that between Nos. 1 and 2 buoys. Approach with caution and look for the tidal flow on the buoys.
Vessels approaching Cowes from the west should note that slack water off Egypt Point takes place approximately 3 hours before High Water Portsmouth.
Tides in the approaches to Cowes can run up to 3 knots. These strong tidal streams have a significant effect on the manoeuvrability of commercial shipping and ferries.
Vessels under 20m, sailing vessels and fishing vessels must give way to large vessels that can only safely navigate within the Cowes Harbour Outer and Inner Fairways.
Just off Nos. 1 and 2 buoys a westerly-going ebb tide runs between HW-2.5hrs and HW+3hrs with maximum rates (up to 2.5 knots on spring tides) around 1 hour after HW. The weaker easterly-going flood tide runs from HW+5hrs to HW-3hrs with rates of up to 1.5 knots on spring tides.
When passing west of the Cowes Breakwater and up to No. 2A buoy you may enter a tidal shadow with little movement.
Between No. 2A buoy and No. 4A beacon from HW-2.5hrs to HW, vessels may experience a cross-current of up to 2 knots at spring tides, which has a tendency to set vessels down towards the western shore. This cross-current splits into two separate flows on the western side of the Inner Fairway (between the Island Sailing Club and the Red Jet terminal) with a current of up to 1.5 knots in either direction.
Small craft transiting between No. 2A buoy and No. 4A beacon should be prepared to alter their heading so as not to be set westwards across the fairway and should avoid impeding the safe passage of commercial shipping and ferries.
Large vessels, including the Red Jets, vehicle and freight ferries, when entering or leaving the harbour during this period may be required to remain towards the eastern side (red buoys) of the fairway between No. 2A buoy and the No. 4A beacon to avoid being set down onto the western shore.
A strong cross current up to 2 knots may be experienced between HW-2.5hrs and HW
At the Chain Ferry, the flood tide can reach 2.5 knots between HW-2.5hrs and HW at spring tides. The ebb tide can reach 4 knots between LW-3hrs and LW at spring tides.
Height of tide
Height of tide is also significant when navigating in Cowes Harbour. Even for craft drawing as little as 1.5m, care has to be taken when navigating in the River Medina above Kingston Power Station with the depth in the fairway up to the Folly Inn as little as 0.7m below Chart Datum.
Passage to Newport, 2 nautical miles south of the Folly, can generally only take place about 2 hours either side of high tide. Craft using the Cowes Eastern Channel, when arriving or departing Cowes Harbour from/to the north or east, can do so at most states of the tide as it is dredged to 2.25m below Chart Datum (check that your draft is less than tide height + 2.25m).
Tide gauges are in place on the Shrape Beacon, at Watch House Slip by the Island Sailing Club (see photo above), at Cowes Town Quay, on the 4A beacon at the west end of the Eastern Channel, and at the north end of Medina Wharf opposite East Cowes Marina.
Vessels using GPS to measure their boat speed must be aware of the effect the tidal stream has on their speed over the ground and ensure that the Cowes Harbour speed limit of 6 knots through the water is not exceeded.