Tidal currents of varying intensity mixed up with fluvial flow after rainfall adds to the complications of sailing at Ranelagh. To quote a senior members with decades of (river-)sailing experience: “If you can sail at Ranelagh you can sail everywhere.”

As a general rule the incoming tidal creates a current flowing upriver for a good 5 hours. The current turns about 20 minutes after high water. With the outgoing tide the current also changes, flowing for more than 7 hours towards the sea. The current tends to turn about 40 mins after low water. However, depending on the volume of rain water coming down the river, it may take considerably longer before the current reverses at low water. And in fact in early 2014 after very strong rain fall, the incoming tidal current never managed to overcome the fluvial flow. Finally, even when the Thames Barrier is closed, there remains a little current in the river.

The PLA provides a nice feature that warns river users about the strength of tidal fluvial flow: