The estuary at Newport contains some large flounders that swim up into the estuary to feed on the mudflats. Bass, mullet, eels and sea trout (sewin) also can be caught although it is illegal to fish for sea trout or salmon without a license. The photograph shows the channels of deeper water. it is worth walking down the estuary on the eastern bank (golf course side) of the estuary to note the bends and gullies. At certain times during the flood or ebb tide there will be strong currents in the deep water channels and, if there has been rain recently, a lot of weed and debris in the water which will make fishing difficult. There is a spot just past the second white cottage, the one between the path and the water, which looks a good spot; I have not fished here though so cannot say what it fishes like. If I can get the time and worm or crab bait I will give it a go and edit this post accordingly.
Do not be tempted to walk far out onto the mudflats, it is gooey sticky (and deep) stuff. Peeler or soft crabs can be found in the intertidal zone if you are lucky.
Mullet can be targetted by float fishing bread or mackerel flesh at slack water over high tide or on the tide ebb tide when an overdepth set up can be trotted down the flow to target flounder and bass as well as the mullet. If you can get near the water level a spinner may take mullet bass or flounder.