Exhibit 99.1 March 26, 2024 On March 26, 2024, C3is Inc. (the "Company") announced its preliminary fourth quarter and twelve months results for the period ended December 31, 2023. • Voyage revenues for the three months ended December 31, 2023 amounted to $13.8 million, an increase of$10.7 million compared to revenues of $3.1 million for the three months ended December 31, 2022, primarily due to the increase in the average number of our vessels. Total calendar days for our fleet were 276 days for the three ...