Flow back into Loch Etive...

as the tide rises through the narrow entrance from the Firth of Lorn (open sea) back into the loch. It becomes turbulent because the tide rises more quickly than the water can flow back over the rocky shelf that forms the Falls of Lora. The falls are generated when the water level in the Firth of Lorn drops below the level in Loch Etive as the tide goes out.

In most situations slack water occurs at high and low tides, in the case of the Falls of Lora, slack water occurs when the water levels are the same on either side not when the tidal change is at its least. As a result the tidal range is much greater on the coast than it is inside the loch. A 3 metre range at Oban may produce only a 1.3 metres at Bonawe on the loch shore.