[3] The construction of the Saemangeum Seawall caused controversy from the moment it was announced as environmental groups protested against the impact of the dyke on the local environment.

Major construction was completed in April 2006, with the seawall 500 metres (1,600 ft) longer than the Afsluitdijk in the IJsselmeer, the Netherlands, previously the longest seawall-dyke in the world.

[citation needed] As of 2019[update] a floating solar PV plant of 2.1 GW capacity was planned using the coastal reservoir area of the Saemangeum Seawall.

[7] Red tides occur almost year round inside the dyke, and even when the sluice gates are fully open the water quality does not improve much owing to the loss of hydrodynamic stirring power.

[7] A study of benthic communities enclosed by the dyke and the environmental factors determining them[9] (where the abundance and biomass of various species of intertidal fauna were measured in 2005) aimed at giving baseline data on the "distribution of benthic macrofauna for future monitoring" and at "identifying the relative importance of environmental variables that explain faunal zonation".