This croc is having lots of fun despite the haze, at Marina East. It is a really nice walk from Tg Rhu, with separate paths for pedestrians and cyclists. You walk about 600m till you past the Marina Barrage. Then you walk a bit more and suddenly you are on this nice open space, with the sea on your right, ships in the horizon, and some people flying kites on your left.
After a while, you will see this map. Onward, follow the narrow trodden path which will open into the vast open space. You will also see a building called Ventilation Building (whatever that is) on your left. The sea is on your right as you enter this open space.