The north-western beach is the sand/shingle/mud estuary
Traeth Dulas (
Dulas Beach); southeast of this is the tiny Traeth Bach (
Small Beach) and the sandy
Traeth yr Ora (
Beach of The Fortified Landing Place). The
estuary running through Traeth Dulas is that of the Afon Goch (
Red River). The Traeth Bach and Traeth Yr Ora at high tide are separated by a rock outcrop called Craig y Sais (
The Saxon Rock). At low tide, however, it is possible to walk on the sand between the three beaches and also onto the beaches of
Lligwy Bay to the south. Traeth Dulas is most affected by the tide, so much so that the most inland parts of the estuary are
salt marshes. A walk is the circuit starting at
Lligwy Bay, taking in Traeth Ora, the Pilot boat Pub and an option to reach the top of nearby
Mynydd Bodafon. About a mile and a half off shore is a small island,
Ynys Dulas, which is roughly 620m long and has a maximum width of 205m. It is known for the
seals which live on the island (hence it is also known locally as Seal Island), but it is too small for human habitation. However, upon this island is a round structure with a cone-shaped top that was built in 1821 by James Hughes to store food and provide shelter for shipwrecked
seamen. Two much smaller islands, Garreg Allan (
The Outer, Expelled or Furthest Stone, not visible by the naked eye from the shore, behind Ynys Dulas) and Ynys y Carcharorion (''Prisoners' Island'', nearer Traeth Dulas) are also present.
Oil tankers can often be seen out some miles from shore in the
Irish Sea, as they wait for the tide to enter the
River Mersey for discharge at
Tranmere Oil Terminal. ==Bathymetry and history==