The area contains huge areas of water plants, that fish use for spawning. Both the billions of plants and young fish attract 10 of thousands waterbirds. Groups of more than 1000 Eurasian Coot, 1000 Gadwall, 1000 Northern Shoveler, or 50 Black-necked Grebe are not uncommon. Red-necked Grebe breeds here and Great Northern Diver (Common Loon) winters every year with upto 3 individuals. During spring migration 1000s of swallows or swifts can use this site as a stopover, especially in adverse weather. Common Goldeneye, Greater Scaup can be found between the many ducks and the area is a major sleeping area for Red-breasted Merganser. The islands hold good breeding bird colonies with Great Cormorant, Great Egret, Little Egret and Grey Heron. Also many Barnacle Goose and Greylag Goose breed there, as well as many ducks. Common Nightingale, Cetti's Warbler and sometimes Penduline Tit breed on the islands. Common Buzzard and Northern Goshawk breed on the islands and wintering White-tailed Eagle are present and several individuals use the area for sleeping.
Go to the tiny harbour of Oude Tonge and from there south towards the Suisendijk. At the end of the Suisendijk the road goes down towards a small recreation field and car park. On foot or by bike follow the cycling path on the dyke to the west. You can continue until the Grevelingen dyke and even beyond.
P.S. good birdwatching starts already before the car park, as the vantage point from the sluices gives a good view on the roosting site of the White-tailed Eagle and the canal and harbour may hold Smew and Goosander.
Access from the other side is also possible: Take the N59 from Oude Tonge towards Bruinisse. Take the turnoff towards Sint Philipsland. At the roundabout take the side road back towards Oude Tonge and drive beween the N59 and the Krammer lake on a small road, the Zuiderlandse dijk. Birding from your car is possible on that stretch, but be carefull, as more traffic uses this road. Continue untill the road turns right (east), away from the N59. Park your car on the right, just before the road bends back towards the left.