High Quality Content by WIKIPEDIA articles! Lagos Lagoon is a lagoon sharing its name with the city of Lagos, Nigeria, the second largest city in Africa, which lies on its south-western side. The name is Portuguese, and means 'lakes' in the Portuguese language so 'Lagos Lagoon' is an example of a tautological place name. The lagoon is more than 50 km long and 3 to 13 km wide, separated from the Atlantic Ocean by a long sand spit 2 to 5 km wide, which has swampy margins on the lagoon side. Its surface area is approximately 6,354.7 sq km