  Autonomous vessels have emerged as a prominent and accepted solution,
particularly in the naval defence sector. However, achieving full autonomy for
marine vessels demands the development of robust and reliable control and
guidance systems that can handle various encounters with manned and unmanned
vessels while operating effectively under diverse weather and sea conditions. A
significant challenge in this pursuit is ensuring the autonomous vessels'
compliance with the International Regulations for Preventing Collisions at Sea
(COLREGs). These regulations present a formidable hurdle for the human-level
understanding by autonomous systems as they were originally designed from
common navigation practices created since the mid-19th century. Their ambiguous
language assumes experienced sailors' interpretation and execution, and
therefore demands a high-level (cognitive) understanding of language and agent
intentions. These capabilities surpass the current state-of-the-art in
intelligent systems. This position paper highlights the critical requirements
for a trustworthy control and guidance system, exploring the complexity of
adapting COLREGs for safe vessel-on-vessel encounters considering autonomous
maritime technology competing and/or cooperating with manned vessels.
