It pays to know the state of tide and which way it ebbs and floods, particularly near reefs and in narrow channels. As mentioned, tide may influence anchored boats more than the wind. Sailing boats with deep keels will generally be more influenced by tidal flow i.e. will face into it, or perhaps lay at an angle to it if the wind is moderate. Power boats with shallow hulls and lots of top-hamper will usually face into wind, with perhaps a bit of angle off the wind if the tidal flow is strong from another direction.
If wind is against tide and both are moderate to strong, the waves will 'stand up' quite vertically and sometimes there is even an illusion that they are running into wind rather than downwind as you would expect.
In these conditions, in the absence of cues from windsurfers, smoke, trees etc, the way waves are breaking along the shoreline or reef is probably the best indicator of approximate wind direction, bearing in mind that wind direction inshore could be deflected by the shape of the local terrain.
Last edited by Mach E Avelli; 13th Aug 2012 at 10:32.