While I do not hunt waterfowl any more, the shotgun I used the most was a M870 Special Purpose with 26" bbls. Synthetic stock was long ago swapped out for an early walnut police stock for a nice upgrade. Theses SPs were some of the very early 870s with a matte finish, but had much nicer finish than the Express. In the end, the Express took the sales and the SP was discontinued.
I bought it new when they were discontinued and still own it.
A Browning BPS 12 ga. Keeps the hulls ejecting downwards in a boat & not rapping a buddy in the head in a blind. I can miss just as well with this gun as any other... An Ithaca would do as well with good screw in chokes.
The relatively newer Ithaca Waterfowl fulfills this criteria.