The Sluice River rises to the north of Dublin Airport and flows in an easterly direction entering the sea at the Baldoyle Estuary. It flows through the townlands of Greenwood, Abbeyville, Kinsealy and Old Portmarnock before entering the sea at Portmarnock Bridge on Strand Rd. The marsh is 600 metres inland from the bridge and extends for a further 400 metres westwards where it borders the railway track and Portmarnock Raceway (trotting track). Malahide Golf Club forms the northern boundary of the site.
Freshwater marsh is comparatively species rich, supporting a high proportion of wetland species in addition to typical dominants: Rushes (Juncus spp), Sedges(Carex spp.) and grasses such as Creeping Bent(Agrostis stolonifera) and Tall Fescue(Festuca arundinacea). The tall Common Reed(Phragmites australis) which form dense cover for birds and other wildlife is present as are the attractive flowering Yellow Iris (Iris pseudoacorus), Meadowsweet (Filipendula ulmaria). Old hedgerow species such as Privet (Ligustrum vulgare), Hawthorn and Briar (Rubus fruticosus) are present as are typical tree species of marshland such as Alder (Alnus glutinosa) and Willows (Salix fragilis/cinerea).
The area supports a wide variety of birdlife as apart from the marsh, reed swamp, woodland and grassland species the area supports a large number of bird species from Baldoyle Estuary (across the road from this display board) which use the area to feed and roost especially during high tides. Brent Geese and waders such as Oyster Catchers and Godwit are frequent visitors to the grassland areas.
In a study published in 2008 wetland bird species observed on the site included Water Rail, Snipe, Sedge Warbler, Grasshopper Warbler. The area also supports Moor Hen, Mallard, Teal, Curlew and Kingfisher. Sparrowhawk and Buzzard are raptors regularly observed in the area surrounding the Marsh.
Otter dropping and footprints have been observed near the railway bridge. Common Pipistrelle and Soprano Pipistrelle Bats are also present as are Rabbits, Hares, Foxes and Brown Rats.
There are 13 species of butterfly present on the site. As expected the area supports a four species of dragonfly including the Common Darter and fours species of damselfly including the Variable Damselfly.