I've wanted to do this one for a while now! Both Plutarch and Suetonius mention this event, although neither goes into much detail.
From what I've pieced together it happened during Caesar's civil war with Pompey Magnus, during a naval battle at Massalia. (During the Siege of Massilia) Our man Acilius would have been one of Caesar's men, and he was likely engaged with the Massiliote fleet as his foes.
Here's a link to the passage in Plutarch's life of caesar, it's in section 16 (note: the translation here is a little different than the one I used in the video). It's also mentioned in Sutonius' life of caesar (section 68) Here
