And here's a charming little account of fording the Taf (Tave) estuary from 1803:
The village, a neat humble place, is snugly situated beneath the “Castle-cap’d hill” in a woody hollow; whence we traversed a lofty ridge, commanding extensive views, to a neighbouring estuary, formed by the Tave near its junction with the sea. As the tide was out, we could not avail ourselves of the ferry, but had ample directions where the water might be crossed; yet, unfortunately, on arriving at the sands, the description of circumstances received for our guidance proved so general, that we were unable to select the route intended; and the broad current ran with such threatening rapidity into the sea, only half a mile distant, that it would have
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been highly dangerous to have ventured in upon hazard. Ignorant how to proceed, and unwilling to return three or four miles for fresh directions, we gladly observed a couple of young women trudging on the sands in a direction toward us. The proper place for fording was now pointed out, where, it was said, the water would scarcely cover our horses’ knees; we deemed it most prudent, however, to let the natives go first, and they accordingly entered the river, using the precaution of raising their drapery. We followed close; but the lasses had considerably underrated the depth of the water, for it took both them and our horses above their middles; yet so carefully were their clothes held up, that not a thread was wetted. On reaching the opposite shore, their petticoats were suffered to descend: my friend and I then looked at each other, passed an observation, returned our thanks to the damsels, wished them a good morrow; and under an overhanging rock of red granite, crowned with the ivy-mantled remains of Laugharne castle, reached the town, an irregularly built little place, seated on a low bank of the estuary.
JT Barber, A tour throughout South Wales and Monmouthshire. 1803 Nichols & Sons
http://freepages.rootsweb.ancestry.com/~wakefield/history/36643-h/36643-h.htm So, historically it was do-able. Searching on 'Tave' rather than 'Taf' I can find several early C19 accounts of crossings. Also, the 1839 Admiralty chart indicates a ford:
http://www.coflein.gov.uk/en/site/519120/details/ford-laugharne How much the sands and channel have changed since then is, of course, quite another matter...