The extraordinarily shallow, narrow, and long inlet restrains the water exchange severely. The daily tidal amplitude is in the order of centimetres, about 1/10 of the tidal amplitude of the supplying Trondheimsfjord. The shallow river connecting Botn to the Trondheimsfjord blocks out more than half of the tidal wave, making the moon-phase driven tidal flood height cycles the primal driving force for the internal water level, with an abnormally small neap flood effect (zero has been observed during lowest neap tides and meteorologically suppressed sea level).