Aground at Devil's Elbow!
It sounds like a Hardy Boys adventure and for beginners like us it feels like one. We were very careful with the chart, but I suspect this shoal wasn’t on the chart. The boat pitched up on an underwater mudbank, and the swift current swung us broadside on to it.
We felt a bit like we were being stalked in the night by a tiger, though in fact on this backwater we were safe.
Using the boat hook we sounded our perimeter, and found that we were in very very shallow water except for astern. The kindle told us that the tide was between high and low, on it’s way to low. We hurried out the dinghy with our stern anchor. It set well and we started to winch it tight. We gained ground but the current kept us from simply floating free. The last fifty feet of our stern rode is chain and we have no chain winch for it. I hauled on it while Kristin reversed.  Repeated blasts like this and we were back into deep water.
Now this deep water was not wide water…  We floated out into the remaining twenty feet between us and a mud island and then downstream til our stern anchor stopped us. We got that up after more labor and passed within a foot or two of the green navigation marker. Free at last.
The process took about half an hour and once the adrenaline was down, seemed more regrettable than terrifying.
We are having a drink in Warren Slough now. The boat is as she should be, tugging at her anchor chain, not perched on the mud.