[gumiel]

No, si sé que no es lo más ortodoxo. Por eso decía que la info que he encontrado en internet es poco clara.

The channel up to Alvor is entered via a 250-metre wide gap through two training walls World icon.png 37°07.08′N, 08°37.14′W. There are lights structures at the ends of both walls, painted with green and white and red and white bands respectively. The deeper water is on the W side of the entrance channel. Although it is possible for a modest draft (maximum 2.0 metres) yacht to navigate the channel up to Alvor at any state of tide, it is best to arrive at half tide and enter with the flow. There is one green buoy inside the entrance which has dragged west and confusingly should be left to port! Another red buoy marks the really shallow part of the channel, but it is still easy to run aground. If arriving on the ebb, note that the tidal current can run at 3-4 knots at springs. Plenty of space to anchor inside the entrance for good swimming, and for deep keel boats to wait for higher water to approach the village.

En cualquier caso, entre cumplir con la norma y tener agua bajo la quilla, prefiero lo segundo.