Avoca Lagoon is located between Cockrone and Terrigal Lagoons. The lagoon has a surface area of approximately 0.63 km2 and a catchment area of 11.6 km2. Much of the upper catchment is rural land, predominantly farm land or undeveloped forest. The immediate North and North-east side of the lagoon lies the suburb of North Avoca and to the South, the suburb of Avoca.
The bed level of the lagoon varies from 0.0 m to 1.5 m AHD (Australian Height Datum), however there are some deep dredge holes down to -4.0 m AHD. As the lagoon is generally closed by the beach berm, the water levels inside the lagoon are not usually influenced by the ocean tides.