As part of the 2022 Russian invasion of Ukraine, Russia mined the waters off the Crimean Peninsula. Russia expected to win its war but when that did not happen some of those mines either broke loose or were cut loose and drifted into shipping lanes used by Ukrainian and NATO ships. So far over 40 of these mines have been found and destroyed. It’s unknown how many are still out there but the NATO countries that border the Black Sea continue to look for them. Some of these mines are bottom mines unlike floating mines, which are kept in place by a chain attached to a weight on the seabed. Bottom mines are placed on the seabed and don’t drift around. This is not a new problem, especially with Russian made floating mines. Since 2017, Iranian naval mines and some crude locally fabricated naval mines have been used off the Yemen coast in the Red Sea. These naval mines are a recognized danger to all ships and in early 2020 shipping companies warned their ship captains that naval mines, of the contact type, were floating into the Red Sea from the north Yemen coast. That coast is off the Shia rebel home province of Sadaa and the rebels had been releasing groups of moored and un-moored mines to disrupt Red Sea shipping traffic to Yemen and Saudi Arabia. The currents generally flow north in this part of the Red Sea, towards the major Saudi Red Sea ports and the entrance to the Suez Canal. The Shia rebels would drop Iranian moored mines into the sea at night. These mines are designed to have their weighted base sink to the bottom of shallow (less than 20 meters) water. Some of these contact mines were released to float on the surface while others had their chains break, turning the moored mine into a free floating one. These mines proved most dangerous to Yemeni fishing boats and similar small craft. Dozens of fishermen were killed when their boats hit one of these contact mines. These mines are a danger to the blockade warships as well as commercial shipping. Most commercial shipping is moved in very large ships which the contact mines inflicted minor hull damage. During 2020 there was a major effort to locate and neutralize these free-floating mines. By the end of 2020 over 160 mines were found and neutralized. The rebels continued putting mines in the water during 2021 and the number found and neutralized remained at 2020 levels. The Shia rebels continue putting these mines in the water. The use of naval mines is diminished because they are not much of a threat to warships (which are constantly on the lookout for them) and commercial ships that are too big to sink with these mines.
The floating contact mines are a 19th century development that has been improved on for over a century and is still used because it is cheap and effective. Iran has acquired a stockpile of 3,000 to 6,000 mines, mostly of Soviet/Russian, Chinese or North Korean origin. Most are unsophisticated but still dangerous moored contact mines, like those that damaged several American warships in the Persian Gulf during 1991. These mines had been released by Iraq. Iran's current arsenal of sea mines is estimated to number around 2,000, and includes the domestically produced Sadaf-01/02 moored contact mines as well as more sophisticated bottom mines that depend on battery-operated sensors to detect ships passing overhead and detonate when a ship of the desired type comes by. These mines put holes in ships’ bottoms, which causes serious flooding that often sinks them. Naval forces with the right equipment can easily find and disable bottom mines and that’s what happened to the ones Iran supplied to the Yemen Shia rebels. The rebels had only a few such mines, and apparently no more were smuggled in after so many were found and destroyed by naval mine clearing ships.