Born 29th March in Meta on the Sorrentine peninsula in the Kingdom of Naples. His father was a chief pilot in the Royal Navy but Eduardo never knew him, as he died a few months after his son's birth. When Eduardo was eleven he went to the Naval academy in Naples and while there also attended classes at the Institute of Fine Arts. He took a keen interest in naval architecture and ship model making.
In 1863 he was appointed a Pilot Grade 3, and in 1864 a sub-lieutenant. Naples had been absorbed into the Italian state in 1861 and this brought frictions in the unified navy. In 1866 he was navigating officer in the corvette 'Ercole' on the South American station, when she went aground near Montevideo. It was apparently the captain's fault but he blamed de Martino, who resigned his commission in disgust in 1868.
He went ashore to live by brush, first at Montevideo, then at Porto Alego in Brazil. Through his friendship with the Brazilian admirals he was presented to the Emperor Pedro II. This resulted in a commission for a number of large paintings of the war with Paraguay 1868-69 and he was dispatched to the theatre of operations in a Brazilian man-of-war. In recognition of his services the Emperor made him a Cavaliere of the Order of the Rose and from then he always referred to himself and was referred to as the Chevalier de Martino. In 1876 he married and moved to London. In 1895 Queen Victoria made him Marine Painter in Ordinary and he was to be the last to hold that appointment. This connection with the court brought him patronage from other crowned heads.
In October 1879 he suffered a stroke, which paralysed him down his right hand side, and though he made a slow recovery his right arm was permanently weakened to the extent that he had to paint with his left hand supporting his right. In 1909 he had a second stroke and, on the 21st May 1912, a third which killed him.
De Martino never offered a painting to the Royal Academy exhibitions because his pride would not accept the possibility that the hanging committee might turn one down; so outside the illustrious circle in which he moved he was not and is not widely known. However, his style brought a new realism, never before achieved, to British marine painting.