Advanced technology has rationalized and simplified operations at sea; however, this development has resulted in higher demands being made of the operator. Good health has become an important safety factor: a good state of health is crucial both to preventing strain injuries and to ensuring alertness and optimal performance at work. Physical activity is a powerful preventive "medicine" for the maintenance of good health and the prevention of overweight and musculoskeletal disorders. The aim of this paper is to analyse the habits and preferences of seafarers with regard to physical activity. Individual health factors, physical activity levels and work-related problems were surveyed on board vessels in a Norwegian shipping company. A questionnaire was completed by 577 seafarers. The results demonstrated that 70% of the respondents exercised twice or more times per week when at home, whereas only 39% exercised on board. Twenty per cent never exercised on board, and 5% never exercised at home. Walking is preferred by 70% of seafarers at home, as well as cycling and doing manual work. On board, walking, cycling and manual work are the most common types of exercise. Strength training is more often preferred on board than at home. Preventing illness and injury, a pleasant and inviting gym on board, and keeping weight under control are the three most important motivational factors. The results show that there is significant potential for improving and organising exercise-related activities on board as a means of maintaining good health and improving the performance of seafarers.