This section describes the W coast of Wales from Wooltack Point to Carmel Head and includes Holyhead Bay, the E side of Saint George’s Channel, Cardigan Bay, and Caernarfon Bay.It also covers the North Coast of Wales and the English coast Northwards to Solway Firth.
Wooltack Point to St. David’s Head
Saint Brides Bay (51°49'N., 5°13'W.) lies N of Wooltack Point and is entered between Skomer Island,and Ramsey Island, 6.5 miles N. It is free from dangers except near the N and S shores. The sea bed is formed of mainly fine sand and mud with excellent holding ground, but the bay is much exposed to provide anything but temporary anchorage. Small craft may take anchorage, sheltered from S winds, in a depth of 6m, within Goultrop Roads, at the SE corner of the bay; however, anchorage is not advised in this area during W winds. ... read more
Streams in the lower part of the estuary can run at up to 5 knots on big springs, not maximum 4 knots as stated.
Higher up the estuary, I very strongly suspect (and I am a local sailing man of many decades standing) that the streams are at least as strong in the Garston Channel, but there is little charted data.
Between Garston and Hale Head the streams can sometimes run at up to 6 knots, but are heavily dependent on the bathymetry of the bottom, which changes frequently.
Between Hale Head and Widnes the tidal waveform is a pronounced sawtooth, leading to very strong streams (and sometimes even a bore) on the flood. At Widnes itself there is on springs a 10 hour ebb, and the entire flood comes in during a period of only about 2 hours.
Wind against tide conditions can produce almost vertical walls of water in stronger winds, both in the main channels and (for different reasons) over the banks; but in light winds the water can be utterly benign.