Follow the thin, twisting channels created by the tidal flow and you're fine, but stray too far and you're stuck fast in silty goo.

For sea traffic the structure could increase the speed of tidal flow.

Fear of litigation, the last refuge of the public-sector jobsworth, had reared its head: police say they feared being sued by anybody involved in an accident in the tidal flow.

Oysters grow in large numbers to form elongated reefs oriented perpendicular to tidal flow in the estuary.

Critics claim that the tidal flow system has not been effective in improving traffic flow.