The setter of this question is being economical with the truth, in order to avoid giving away the answer.
The full name of this swimmer is Eric Moussambani Malonga. He comes from Equatorial Guinea, and the principal official language of that country is Spanish. As any quizzer (not least any who's ever used Wikipedia) should know, the convention in Spanish–speaking cultures is that people are known mainly by their father's surname, and in formal contexts (for example on official forms) that is followed by the mother's birth surname.
Eric the Eel's full name is Eric Moussambani Malonga, but he's better known as Eric Moussambani.
To refer to him as Moussambani Malonga is equivalent to referring to Sergio Agüero as 'Agüero del Castillo'.
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