Finally the sea had overwhelmed Atlantis, and had thenceforward become unnavigable owing to the shoals which marked the spot.
It is thus unnavigable except for small coasting and fishing boats, and sea-going vessels proceed through the Memeler Tief (Memel Deep), which connects the Baltic with Memel and has a depth of 19 ft.
From Shigatse, which stands near the mouth of the Nyang Chu, to the Kyi-chu, or Lhasa river, there is no direct route, the river being unnavigable below Shigatse.
Mainly unnavigable and of little use for irrigation, the Orontes derives its historical importance solely from the convenience of its valley for traffic from N.
The Nam Pawn is a large river, with an average breadth of 100 yds., but is unnavigable owing to its rocky bed.
Pascagoula and Point aux Chenes bays; separated from it by the shallow and practically unnavigable Mississippi Sound is a chain of low, long and narrow sand islands, the largest of which are Petit Bois, Horn, Ship and Cat.