Tidal currents?

I am wondering what these are?  I am referring to the river-like surface phenomenon we have probably all noticed on Puget Sound.  It is a linear feature of less wind-rippled water, often with detritus.  For a long time I assumed these were tidal currents, but now I am not so sure.  I am sure they are related to the tide because they change over time.  Paddling around on the kayak has been the first extensive boating experience for me, and paddling around alone on the kayak with the depth finder has caused me to ponder what I see.   I am beginning to think these currents are not currents at all but upwelling caused by underwater contour.  Tidal flow hits a canyon wall or steep incline and some of the water is diverted up.  The welling smooths out the wind ripples like collagen smoothing wrinkles and the detritus is loose stuff brought up from the bottom. 

Does anyone have a definitive answer?

I believe that you're describing current seams.  Sometimes they're a result of nearby underwater features and sometimes they're a result of the shape of a bay directing current flow in multiple directions.  Regardless of the cause, these are the areas you want to concentrate your efforts.  Bait fish will concentrate in the current seams and the big fiddies will be on the edges looking for an easy meal.

When the current is moving in the same direction as the wind, especially if it is close to the wind speed, you won't see much in the way of (wind) waves. The same current and wind speed opposing each other will kick up waves. it's a good idea to watch out for the potential of bigger waves after a tide change, especially in the vicinity of points (tide rips).

Like rivers, you will see current/eddy seams, as Spot mentions. Seems like the weeds stack up on the eddy side of the seam. I usually try to fish the current side of the seam, which is often (but not always, depending on wind and current direction) the rougher side. The salmon are looking for disoriented bait getting shoved around in that faster water.

There are some good ones in the San Juans. In July I found a 6-8kt rip off the South end of Cyprus. It's clearly marked on the chart, but that requires looking at a chart before you go to know that! It swallowed my boat as I ferried across it. Submerged the whole thing under about 6 inches of water.

If you want to see one of the best tidal races in the PNW. Google Skookumchuck Narrows or Okisolo tidal rapid.

Nothing like surfing a standing wave for hours on end!