Iran has announced that it will deploy "light" submarines to the Caspian Sea, yet another step in the ongoing militarization of the oil- and gas-rich sea.
The deputy commander of Iran's navy made the announcement (in late June, while The Bug Pit was on hiatus) but gave no details. Some Azerbaijani officials believed (or at least were telling reporters) that Iran already had submarines in the sea, and that a semi-famous photo of Iranian President Mahmoud Ahmadinejad getting into a sub was taken on the Caspian. Given that Iran is a lot more likely to overstate its capabilities than understate them, that latter claim probably wasn't true, and we should take this new claim with a grain of salt, as well.
Nevertheless, if Iran's newest oil and gas discovery, in waters also claimed by Azerbaijan, turns out to be for real, it would be natural for Iran to beef up its defenses around the sea.