Loch Ness is "Locked" at both ends...Inverness and at Fort Augustus at western end. It used to be land-locked until the locks were built. At western end the locks take boats into Loch Long and Loch Lochie before exiting to the sea at Loch Linnie and Fort William, if I remember correctly.
Scotland has both fresh water lochs, as in Loch Lomand, and salt water lochs, as in Loch Linnie. The above three, mentioned first, are all part of the Caledonian Canal, which effectively splits Scotland in two.
Ian