Due to the growing rivalry between local and external actors, the Indian Ocean region is increasingly the site of an underwater Cold War. India and Pakistan are actively developing their submarines, contributing to regional maritime saturation. While India plans to increase the number of conventional vessels and nuclear-powered submarines armed with nuclear-capable ballistic missiles, Pakistan is working on launching nuclear-capable cruise missiles from diesel-electric submarines. This maritime saturation leads to the emergence of new threats and the revitalisation of old ones. The danger of accidental collisions between nuclear-powered submarines and diesel submarines, in some cases both with nuclear weapons on board, is increasing. Mutual misunderstanding of strategic imperatives and mistrust can lead to accidental conflicts, and incidents on board nuclear submarines. This essay argues that it is necessary to raise awareness of these challenges and of strategic cultures in the region to prevent incidents with nuclear weapons.