Background: The aim of this study was to screen for musculoskeletal disorders (MSD) complaints, to analyse the activity and to identify their risk factors. Materials and methods: This cross-sectional epidemiological study involved 903 men aged > 20 years and with a seniority > 2 years. It included a questionnaire and an ergonomic analysis of the activity. The questionnaire included: socio-demographic and occupational characteristics, health status and life habits, stress and items from the Nordic questionnaire. The observation of work situations required video recordings and the use of three methods: Occupational Safety and Health Administration (OSHA), Rapid Upper Limb Assessment (RULA) and the Gesture Tracking and Assessment Tool (Outil de Repérage et d’Évaluation des Gestes: OREGE). Results: The prevalence of MSDs was 61.9%. It was significantly higher among deckhands than among other professionals (65.6% vs 27.4%; p < 0.001) and in seasonal workers than in permanent workers (67.8% vs 43.1%; p < 0.001). A positive correlation was noted between MSDs and daily work duration. Stress was an aggravating factor, whereas leisure activities were protective. The prevalence of MSDs was 40.5% (lower back), 40.4% (wrist/hand joints), 34.6% (neck) and 31.7% (shoulders). The ergonomic analysis of the workstation was performed on a deckhand who unloaded the fish crates out of the hold of a trawler. OSHA score = 12 (normal < 5); significant risk of upper limb MSD. RULA total score = 7 (acceptable between 1 and 2); immediate modification. OREGE scores evaluating effort, repetitiveness and joint positions indicate that the actions were not recommended or to be avoided. Conclusions: The analysis made it possible to evaluate the difficulty of the job and to note a high risk of MSDs requiring ergonomic and organizational improvements.