Nigeria doesn't have a sea in it. I'm not sure what you are asking so I will give you two answers. Nigeria borders the Gulf of Guinea which is part of the Atlantic Ocean. Lake Chad is the largest lake in Nigeria.
No, the Atlantic Ocean
The Atlantic Ocean lies to the south of Nigeria. To the east, west, and north of Nigeria is land, occupied by its neighbor African countries.
The highest point in Nigeria is Chappal Waddi, which is 2419 meters (or 7936 feet) above sea level.
Assuming there is a prophet in Nigeria you could travel by air, sea or overland, depending on your starting point.
by plane and boot by sea
Nigeria is not surrounded by an ocean but bordered at the southern most part of the country by the Atlantic Ocean. Otunba.
Nigeria is situated in West Africa. The coordinates for Nigeria is 10°N, 8°E. Nigeria is bordered on the west by The Republic of Benin, to the north by Niger and Chad, to the east by Cameroon and to the south by the Atlantic ocean.
Canada is surrounded by the Atlantic, Pacific and Arctic oceans and the Great Lakes. The Pacific Ocean and China Seas border China. Kazakhstan borders the Aral Sea and the Caspian Sea. The Gulf of Guinea and Atlantic Ocean border Nigeria. The Atlantic Ocean and the Mediterranean Sea border Spain.
The lake located on the border of Chad, Niger, and Nigeria is the red sea
The largest country in Africa by population is Nigeria with a population of 135,031,164
That point is in the sea off the coast of Nigeria, about 45 miles southeast of Cotonou, Benin.