There are good sites to the north and south of the map which I like to visit given time but there are plenty of places to keep you busy for a day within this area. Tides are a major consideration and local tides can be checked here along with how to catch breakfast, lunch and dinner if you have a boat.
Perhaps this ray had been caught out by the dropping tide and was thrashing about in the shallows of a tidal river.
In winter there are huge rafts of diving ducks off-shore, mainly Greater Scaup but with large numbers of Red-breasted Merganser and Goldeneye as well as Great Crested Grebes, unfortunately well off-shore (especially at low tide) due to the shallow slope of the bay, though they do come up the channels cut by the numerous rivers. Depending on the weather Streaked Shearwaters can often be seen moving off-shore too. Close inshore there are large numbers of dabbling ducks, particularly Eurasian Wigeon, Gadwall and Falcated Duck.
From the south side of the Komozu River at high tide; mainly Eurasian Wigeon with a few Falcated Duck and Gadwall. From the Kyoto birders perspective the Black Brant in the centre and a couple of Common Shelduck at the back would be the highlights here.
The Komozu River (the one at the top of the map) is better on a rising tide and usually waders are closer when viewed from the northern side, however if high tide is early in the day, looking into the sun will be a problem. The southern side of the rivermouth (marked Tsumatsusaka Port on the map, even though there's no harbour there) is also an excellent view point, though most waders tend to be a little more distant. The occasionally a kite-surfer off the river mouth will make you want to beat your head against the seawall. It's possible to drop down onto the fields here and if there are any wet areas before flooding for rice planting becomes widespread, they can be fantastic for waders. In any case this area is the best bet for Long-toed Stint, Pacific Golden Plover and the larger migrant snipe. I've also found Richard's (April) and Red-throated (winter) Pipit here. Getting back onto the seawall gives the best views of the large pool at the southern corner of the fields. Hundreds of ducks congregate here, mainly loafing Greater Scaup coming off the sea but it's too deep attract waders other than the odd longer-legged Common Greenshank or Black-winged Stilt.
Long-toed Stint and Wood Sandpiper are two species frequently found on flooded fields.
Following the seawall round you'll cross a small river onto the next block of reclaimed land, the pools behind the seawall here are less deep and much better for waders. The low trees that line this road seem to have migrating Chestnut-eared Starlings every time I visit in spring! Continuing south along the seawall, the mudflats on the left are the most expansive on this stretch of coastline. However the lower the tide, the greater the number of shellfish diggers that will be active. With diggers both slightly ahead of and dotted behind the falling tide, there's little space for waders to settle and most will look elsewhere. So days with less pronounced tidal fluctuation will mean fewer shellfish diggers (often none), and obviously be better for birds. You'll see Matsusaka Port across the bay and it's possible to follow the coast most of the way around but the next important area is just to the south of the port where three rivers empty into the sea.
Grey-tailed Tattler can be very common but it can also be surprisingly easy to miss lurking at the foot of the seawalls.
Greater Scaup and Great Crested Grebe in Matsusaka Port.
On the south side of the port there are some grassy sandbars just off the river mouths and beyond that many bamboo poles planted in the mud. In August and September Crested Terns arrive along the Pacific coast of western Japan and I've seen as many as 30-40 dotted around on posts here.
One of many Crested Terns on posts planted in the bay. Great Cormorants, Great White Egrets and Black-tailed Gulls are always numerous. Behind them is the high-speed shuttle from Matsusaka to Nagoya Airport.
I suspect many waders roost out of sight on the grassy sandbars at high tide as when the water drops birds instantly begin to appear. Unlike most sites waders actually get closer as the tide falls, the waterline recedes from the sandbars exposing more of the sandflats towards the observation points (whether on the north or south side) bringing the waders with it. On a rising tide it's best to head further up the estuary where an area of exposed mud lingers. Saunder's Gulls can be seen very well from the road in winter as they fly back and forth over narrow strips of mud along the south side of this estuary. This area also suffers a lot of disturbance from shellfish diggers so again it's more productive on days where the tidal drop isn't so great and there'll be fewer diggers.
Oystercatcher and Bar-tailed Godwits higher up the river while high tide still surrounded the sandbars.
Leaving the coast a little, following the rivers upstream, the riparian habitat is good for several bunting species including Chestnut-eared (low density makes this the most difficult of the local buntings to find), Green Pheasants are common but Chinese Bamboo Partridge and Ruddy Crake require a great deal of patience or luck. Oriental Reed Warblers become common in April and Zitting Cisticola is reasonably common year round.
The above map shows a couple of river mouths in Tsu city, really the only area easily accessible by public transport as it's only a short walk from JR and Kintetsu train stations. In winter the area is good for ducks, Oystercatcher, sanderling and Ruddy Turnstone. The latter two are more reliably found in this area an those previously mentioned.
Leucistic Vega Gull on the Tsu city sea front.
Two or three kilometres further north the beaches attract large numbers of gulls and more northerly species like Glaucous are more regular here than in the Osaka area. Scrub behind the beaches looks attractive for migrants but in a small number of very brief visits in suitable seasons I've never found anything of real interest. Though there was a wintering Shore Lark there one winter.
There are several other excellent areas for waders and terns around the huge Ise Bay, particularly at the head of the bay, and of course the Atsumi Peninsular is famous for its autumn raptor passage.