Objective: This study employed Computational Fluid Dynamics (CFD) analysis to investigate the fluid resistance characteristics of different drafting positions in marathon swimming, providing theoretical guidance for selecting optimal drafting strategies in competitions and training. Methods: Multi-swimmer models were established using 3D body scanning technology, and different formation models (I-type, A-type, V-type, L-type, and H-type) were created by adjusting the lateral and longitudinal distances between individual swimmers. The ANSYS Discovery Live software was used to simulate the overall resistance of different models and the individual swimmers within the formations. Results: The I3 formation had an overall drag reduction effect, reducing total resistance by 55.21%, while other formations increased overall resistance. The V-type formation had the highest increase in overall resistance (31.88%). During drafting, the position with the least resistance was the end position in the I3 formation; the position with the highest resistance was the middle position in the L-type formation (51.1±18.0 N, P<0.05). During leading, the leading swimmer in the A-type formation (48.2±20.5N) experienced significantly greater fluid resistance than when swimming alone , P<0.05. Conclusion: The drag reduction effect of longitudinal drafting formations was superior, with the end position in a three-person longitudinal arrangement having the best drag reduction effect. Considering both tactics and drag reduction effects, it is advisable to avoid swimming in the middle position of lateral formations.