The Euripus was closed by a dike of coarse sediment until about 6000 years ago, when it was opened by an (unrecorded) earthquake. Herodotus mentions the strait during his description of the Battle of Artemisium (480 BC), with the account implying that it was navigable by large fleets of triremes. Diodorus Siculus reports that in 411 BC the Euboeans closed the strait by mostly rebuilding the dike, with the goal of making themselves part of Boeotia, therefore not an island subject to Athenian hegemony. Diodorus states that gaps had to be left in the dike to allow the Euripus tides to flow through; the narrowness of the remaining passage made the current much more intense. Only a single passage was left navigable, just wide enough for a single ship. There is no mention of the closure of the strait in either Thucydides' "History of the Peloponnesian War" or Xenophon's "Hellenica". Strabo wrote that at an unspecified later date the strait was crossed by a bridge two plethra long (approximately , which is probably an exaggeration). Some vestiges of the artificial dike probably remained, so the gap spanned by the bridge could have been narrower than the channel that existed before 411 BC. Ancient historians do not record the depth of the channel; even the passage under Strabo's bridge may have been scoured by the tides to a depth sufficient for ancient shipping.