Water depth certainly has a big part to play especially in areas where the seabed is gently sloping or there are large shallow areas offshore, less so in more exposed coasts.
Wave current interaction is a fascinating part of physical oceanography, its also a total mind fvck when you tr and consider it in practice. currents can refract waves, shift them in frequency space and dissipate wave energy - to the extent waves can be completely blocked if an opposing current approaches the wave group speed.
In south wales its very complicated, the currents are strong enough to approach a blocking scenario on the outgoing tide or a least significantly reduce wave heights, hence why it can be completely flat on the drop and 5ft on the push, then you've got the sandbars which block swell to some places at low tide, and the fact that theres strong longshore currents and curent gradients will refract the waves such that the angle of incidence changes. I can think of a couple of places that have good quality rights with the tide in one direction and good quality lefts with the tide in the other!
For the scientifically minded: http://www.thereefjournal.com/files/2._ ... George.pdf