Cyber threats and electronic interference can sink projects before they even set sail. What are the key cybersecurity risks and vulnerabilities, and how can they be mitigated? The presentation offers three real-world cases where Mahi detected, resolved and reported security flaws in communication devices and navigation sensors. These findings highlight the critical need for secure-by-design navigation systems to ensure continuous and reliable operations in uncrewed and lean-crewed vessels. The Baltic Sea jamming crisis and rising geopolitical tensions reveal further vulnerabilities in autonomous systems. The presentation outlines mitigation strategies to counter jamming-induced paralysis, spoofing-driven navigation errors and direct cyber intrusions.