Water-Borne Improvised Explosive Devices (WBIEDs) have been in use as an asymmetric warfare tactic since at least the early 1970s. The most famous incident involved the successful detonation of a bomb-laden skiff against the USS Cole on October 12, 2000 in the Yemeni port city of Aden. Since then, few notably successful WBIED attacks have occurred which would threaten the maritime status quo of military, commercial, and civilian transit. Nevertheless, growing Iranian influence has precipitated the use of WBIEDs amongst many of their proxies abroad, most notably the Houthis in Yemen, Hamas and the Palestinian Islamic Jihad in Gaza. There is evidence to suggest that while few WBIED attacks by Iranian proxies have proven successful, increasingly sophisticated and now unmanned WBIEDs will continue to develop as a mainstay of tactical options amongst members of the Iranian Threat Network (ITN).
In 2015, the Iranian government released a series of animated videos which demonstrated the use, or would-be use, of water and airborne IEDs against a sizable US carrier fleet. These videos then suggested that swarm-tactics, suicide or unmanned, were considered both a tactic of national defense, as well as an option for aggression-by-proxy. The former proposition seems to have been abandoned in light of Iranian ballistics and naval development since 2015, indicated further by their missile attacks on Israeli cargo vessels transiting the Strait of Hormuz in late 2020 and early 2021. Use of WBIEDs by proxy however, remains a notable tactical element among Iranian-backed militant groups.
The most notable event within recent conflict indicating the advancement of WBIED technology was the thwarting of a Hamas unmanned submarine-bomb, controlled by mobile Hamas command and control elements driving around Gaza City, in May of 2021. The fully-submersible craft housed a 30kg (66lbs) explosive device, and is believed to have been bound for Israeli Naval vessels. The Israeli Defense Force (IDF) released a video shortly after the event showing the destruction of the submersible. This event represents a significant leap from the unmanned surface-based WBIEDs utilized by the Houthis against Royal Saudi Naval forces since 2017, such attempts by the Houthis have proven largely unsuccessful due to radar detection and close-in weapons systems (CIWS). Newer and more advanced WBIEDs however, demonstrate the tell-tale signs of Iranian influence and technical assistance in their planning and construction.
Thus far, surface radar, CIWS, and radio interception for sourcing WBIED command and control, have all proven vital in mitigating the WBIED threat. Radio tracking and signal intelligence in particular have been of supreme importance because in targeting a single command hub, a swarm of multiple threats may be neutralized in future engagements. Targeting command and control elements may also discourage extremist groups from using the tactic, as they realize the anonymity of unmanned weapons does not necessarily grant them increased safety. Concerned nations should seek to develop the capabilities to detect unmanned, surface and sub-surface naval vessels, as well as their control elements, while extending such protection to oil platforms and civilian vessels under their maritime aegis.
Coastal monitoring, and security buffers between coasts and sea-lanes are both crucial if the WBIED threat is to be actively deterred. It is reasonable to assume that unmanned WBIED capabilities will continue to grow among Hamas, Palestinian Islamic Jihad, Houthi rebels, Hezbollah, and other Iran-backed militants seeking to target military, commercial, and civilian vessels within range of coastal launching zones. Iran’s overarching goal through the proliferation of WBIED equipment, technology, and training, is best summarized as low-level retaliation against stronger adversaries (Israel and the US), and the harassment and enervation of relatively equal naval powers (Saudi Arabia) in the regional maritime domain.