[1] Diamantidis qualified for the men's 1500 m freestyle at the 2004 Summer Olympics in Athens, by clearing a FINA A-standard entry time of 15:09.25 from the Greece National Open in Thessaloniki.

[2] He challenged seven other swimmers on the fourth heat, including top medal favorite Larsen Jensen of the United States.

He rounded out the field to last place by a 27-second margin behind Italy's Christian Minotti in 16:06.31.

Diamantidis failed to advance into the final, as he placed thirty-first overall in the preliminaries.

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