A lengthy piece in the Persian Journal casts (well known) doubts on Herodotus' trustworthiness and goes further to deny that Thermopylae (and Salamis too) ever happened. Inter alia:

According to Herodotus, hundreds of Persian ships were sunk at Salamis. Where are the remains of these shipwrecks? Of course, not all shipwrecks are always salvaged, either because the exact site is indeterminate, or because a single ship is being sought. The location that is given by Herodotus is a relatively precise location, and is not in a desolate or extremely deep part of an ocean. It is close to land, and not too deep. So what has been found at the site? Not much. Apart from an occasional shipwreck or two from the ancient world, the vast graveyard of triremes one expects to find there is notably absent, even with today's complex ship salvage technologies.

How about Thermopylae? What has been recovered there? Apart from some Persian arrowheads, not much else. Again, considering the very specific site of battle and mountainous terrain that allows for only a small strip of flat land, the search area is relatively small. Furthermore, it is unlikely that it would conceal the following from the prying eyes of modern archaeologists:

"It was while they were at this station that a herald reached them from Xerxes, whom he had sent after making the following dispositions with respect to the bodies of those who fell at Thermopylae. Of the twenty thousand who had been slain on the Persian side, he left one thousand upon the field while he buried the rest in trenches; and these he carefully filled up with earth, and hid with foliage, that the sailors might not see any signs of them." Herodotus, The Histories, Book VIII.

Twenty thousand Persians died at Thermopylae, of which nineteen thousand were buried in mass graves at that very site by Xerxes, according to Herodotus. There are supposedly mass graves of 19,000 dead warriors there, somewhere in that narrow mountain pass. Archaeologists have been able to find a few arrowheads from that incident, but the colossal cemetery has somehow managed to elude discovery.

The conspicuous absence of hundreds of sunk Persian ships and the mass graves of 19,000 dead Persian warriors sheds serious doubt not just on the details of Herodotus' story, but upon its entire foundation.

... you can read the whole thing here.

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Tim writes:

My daughter and I watched '300' and loved it, fully aware that it was based largely upon a graphic novel.  But I read that piece in the Persian Journal and can't help wondering if the writer was just that little bit biased.  It's also a bit rich seeing as countries in that part of the world have a tendency to historical revisionism themselves.  Neither does he know much about maritime archaeology as his commentary reveals as, considering how many ships plied the waters of the Med for the past several thousand years, the remains of such are pretty few and far between because survival of such remains are dependant upon so many factors, so I'm not in the least bit suprised at the dearth of Persian shipwrecks. 

I just remembered this link this week as well: The Persian War Shipwreck Survey homepage ... needs some updating, but still applicable.