How do you fly fish the surf?

[dudley]

I fish the surf a lot here in New England, both deep and shallow beaches.
In both cases you need to work with the waves and current rather than against them

On a deep beach, the game fish will search for bait in the trough between a sandbar and the beach,...basically right at your feet.
Water from breaking waves needs somewhere to go so there is often a "longshore" current that runs parallel to the shore, often for some distance before there is a break in the bar structure that allows the water to escape
Baitfish, confused by the breaking waves get trapped in the current and gamefish will ambush them at convenient structure or cruise and pick them off.
Being able to "read" the beach is jut as important a skill as being able to read a trout stream. Being able to keep in touch with your fly is also extremely important

In our area, shallow beaches are often best fished in low light and most often with a floating line.
Most of the time waves travel at somewhat of an angle to the shoreline.
Wading out to a point where you cast cast parallel to the wave direction will give the best presentation.
Make your retrieval at a speed that will keep your line in the trough between waves, so it does not ride up, causing slack
Look for structure such as "points" and "bowls" no matter how slight
These areas can hold bait.

You could write a whole book about this stuff, but the best way to learn is to just go out and do it.
Read the water, watch the bait.... the fish already know their part