The paper presents the results of research on the level of the hardiness of participants of high sea cruises implementing the idea of sail training and being a non-standard form of informal education in practice. The study involved 123 people, including 65 girls and 58 boys aged 13 to 18 years, who can be perceived as youth with special educational needs. They were participants of the Krzysztof Baranowski School Under Sails in 2015 and 2016, the cruise of the 42 Author's High School in Warsaw from 2016, the Catholic School Under Sails in 2017 and Gdańsk School Under Sails in 2019. Method: Pre-posttest study with questionnaires issued on the first and last day of each cruise. Dispositional Resilience Scale was used to measure mental hardiness, commitment, openness to challenges and a sense of control of participants. T-tests were used to check the significance of change in results. Results: The results show a statistically significant increase in hardiness level measured using the Dispositional Resilience Scale. There was also a significant increase in commitment, openness to challenges and a sense of control of participants, which are measured by subscales of the used scale. Conclusions: It can be thought that various types of Schools under Sail are an attractive way to adapt to the special educational needs of gifted young people and strengthen the hardiness of young people, which is a valuable asset of sail training.