Here's my view:
1. A float, even a short one, requires a plume field. And a continuing one. We should continue to see garbage floating in from the dump via the same processes that got the money there in the first place.
2. The dredge explains the bundle being intact without a plume field, or at least only a small, contained one if the FBI is to be believed about thousands of shard being found in the soil underneath the three bundles and radiating out twenty yards.
This begs a second question: why were the three bundles on top of their plume field? Was it the last to arrive? Also, it seems odd that the bundles were central to the plume field. I don't know how that could happen. Honestly, to me it suggests a federal cover story not steeped in physics or hydrology.
In addition, how the bundles got into the dredge, I don't know. Maybe the whole bank bag was down there, and all that thrown up to the beach was this little bit.
That's why I like the Human Hands scenario. I don't think it was planted to be found, unless the feds - or whoever - planted hundreds of bundles in sites all around Cooper Country and none have been found other the one in T-Bar. I suspect an intensional planting for very unusual reasons.