Don't try crossing any mud, no need to anyway.
Fish the beaches at East Portlemouth side. You can park and fish at Mill Bay.
Salcombe side try North and South sands. Carpark at North sands, small carpark at South sands.
Higher up the estuary try the water pumping station which can be found as you leave Kingsbridge towards Charleton on the right down a small slip road. (If you get to the bridge you have gone too far).
Get an OS map and fish Holwell Point, its a bit of a yomp but I see a lot of people fishing it so It must be worthwhile.
Heard of Bass caught off the slip at the end of the main carpark on the quay at Kingsbridge.
Bait and advice available at Devon Angling in Chillington but check opening hours.
Lug, razor, peeler etc.
Torcross may be worth a go for something different.
Good luck and let us know how you get on.
Cider