i don't have any local knowledge, but have watched traffic go by in this location for a few days when staying in a condo on one of the city wharves. Look at the river at, above, and below Penn's Landing:
And you'll see that while the 40' channel (unmarked by buoys) is indeed close to the city wharves, the river is at least 25' deep bank-to-bank, and is a pretty wide river at that.
So, what do the Inland rules actually say? Rule 9 tells small vessels (under 20 meters) to avoid vessels that can navigate only on the "narrow channel or fairway". The empty barge wouldn't have drawn much at all, and the tug, not over maybe 10-12 feet. So, for neither vessel is this a "narrow channel", at least in a legal sense, i would think.
And while Rules 9(a)(ii), 14(d), and 15(b) give the downbound vessel the right-of-way over upbound, or any vessel going up or down river right of way over a crossing vesse, in certain rivers and the Great Lakes, the Delaware River isn't one of these rivers or waters.
So i think we're left with Rule 18, which (logically) gives right of way to "a vessel not under command", meaning one whose engine has broken down. And we're also left with Rule 5, which requires a proper lookout by sight and hearing, and rule 7 which requires vessels to use all available means to determine if they are in a risk of collision. And the Bridge-to-Bridge Radiotelephone Act, which requires most commercial vessels to carry, and monitor, their radios.
Another section of Rule gives right of way to a vessel "restricted in her ability to maneuver" over other vessels, *except* those "not under command. So the Duck is still privileged, i would think. And the tug and barge, while no doubt not nimble and quick-turning, would likely *not* meet the legal definition of "restricted", or else they should have shown "restricted" day shapes, and been giving Securite broadcasts periodically.
None of this changes the common-sense wisdom of "might makes right" or the "law of displacement", which wisely counsel small vessels to stay well clear of big ones. But legally, it's difficult for me to understand how the duck wouldn't have been privileged over the tow, under the rules.
That said, I don't know the details, nor how the vessel tracklines leading up to the collision.