a spit
Tidal power is harnessed by constructing a dam across the mouth of an estuary or a bay.
As far as I know, A river's mouth is simply called the 'river mouth'!
baymouth bar
The medways mouth is at The Thrust Estuary
Yes
The Humber Estuary.
an estuary
estuary
like the mouth of a river
firth mouth embouchure
an Estuary
Thames Estuary.