Cruise lines are adopting onboard quarantine as part of emergency response measures to the global pandemic. However, little is known about the social support embedded in the social-mediated communication process to assist passengers in coping and building resilience. Guided by the conservation of resource theory, this study adopted the netnography approach to analyze the online interactions between quarantined passengers on Diamond Princess and netizens. A qualitative approach was employed to analyze the content of a relational dataset consisting of 14 research subjects, 3,368 posts, and 67,964 comments. The results not merely showed the changing foci of the comments over time but also revealed the supporting role played by social media. The constant engagement with netizens provided passengers with information and social support, which contributed to their coping and resilience-building. These findings offer a new theoretical perspective on incorporating social media in tourism crisis management, as well as practical implications for cruise lines and tourism organizations to optimize their resource utilization for marketing recovery.