Neva Bay
The gulf has an area of . The length (from the Hanko Peninsula to Saint Petersburg) is and the width varies from near the entrance to on the meridian of Moshchny Island; in the Neva Bay, it decreases to . The gulf is relatively shallow, with the depth decreasing from the entrance to the gulf to the continent. The sharpest change occurs near Narva-Jõesuu, which is why this place is called the Narva wall. The average depth is with the maximum of . The depth of the Neva Bay is less than ; therefore, a channel was dug at the bottom for safe navigation. Because of the large influx of fresh water from rivers, especially from the Neva River (two-thirds of the total runoff), the gulf water has very low salinity – between 0.2 and 0.3 ‰ at the surface and 0.3–0.5 ‰ near the bottom. The average water temperature is close to in winter; in summer, it is at the surface and at the bottom. Parts of the gulf can freeze from late November to late April; the freezing starts in the east and gradually proceeds to the west. Complete freezing usually occurs by late January, and it may not occur in mild winters.