Ray -
These are fun, don't get me wrong but on the line-trim challenge I dunno if the edges of things could cut butt material effectively... I'm surprised you didn't mention bic lighters and matches for those who carry them - an easy way to trim for the cautious user.
As far as this question, flats -
The upper cape really has very few flats people would wade, in fact I am hard pressed to think of one. Inside some of the ponds, perhaps but none are as long as you say. Perhaps you mean the two predominant flats areas on cape - the bayside from Barnstable Harbor to Welfleet, then on the other side around the Monomoy Islands and South Beach?
If you are on the bayside or Monomoy without a compass, you are a fool, plain and simple. I even carry a whistle, cell phone, CO2 PFD and lots of other essentials like water. I've even drove landscaping stakes into the clam shoal to learn the high points after a big storm (used to shore guide on these flats).
But you call the shots on the challenge, Regis - and without a compass there I stand in the imaginary fog...
First of all, the water is NOT rising 6" every 15 minutes. You get at least 1/2 hour of slack, often more. The tide current accelerates a certain percentage into the flood, about an hour. So that means starting at two of the drop, you'd have slack low and a soft flood at the start (notwithstanding weather conditions). All this doesn't mean much because fishermen never leave until the water comes barrelling in, and the fish always come in with it. This is the kiss of death on the flats.
The notion that current direction indicates anything is unreliable. It makes all kinds of sweeping direction changes on the flood depending on the channel structure. I would not trust it at all unless like Al mentions, you have direct and recent knowledge of the tide flow direction in that location - even then the reverse tide flow is not always the inverse of the drop. I would not trust the current flow direction and use it only as a (discardable) contributing element in the decision process.
On the bayside, the sun will tell you which way you are going. Even in the thickest fog you will be able to determine the direction of the sun. Most of us have a watch, you did NOT exlude that - so using the time and the position of the sun you can estimate the cardinal direction (NSWE) and head quickly south. On Monomoy, know where the land mass is and act accordingly. The picture I posted on the Monomoy article is about the thickest fog I've seen on the east coast, and the sun is clearly visible.
PREVENTION IS WORTH ALL the hypothesis in the world. Take it from someone who has shore guided the flats for a few years - do not go out there without a compass and a large dose of awareness - on the way out, and on the way in.
Good discussion Ray!