Performance when gliding in the streamlined position depends on a swimmer’s morphological characteristics, body orientation and water characteristics. The purpose of this thesis was twofold. First to identify and assess the effect of controllable factors that contribute to glide performance and second to form the foundations of an improved approach of simulating the fluid flow around the swimmers’ body. To address the purposes of the thesis four investigations were conducted. Study 1. The effect of the head position on glide performance was investigated. When the high, medium and low head positions were compared, it was found that swimmers experience significantly greater resistance and decelerate faster when they adopt a high head position. It was also found that there is no significant difference between the medium and low head position indicating for the first time that swimmers can choose any of the positions according to their natural tendency. Study 2. The second study examined the effect of gliding depth on gliding performance. A range of depths was investigated ranging from 0.8 m to 0.2 m from the water surface. The results demonstrated significantly higher glide factor values for glides at a greater depth when compared to glides closer to the water surface highlighting the retarding effect of wave drag when gliding close to the surface. The optimum gliding performance was reported for glides at 0.8 m from the surface. Study 3. The third study investigated the effect of full body swimsuits on glide performance. According to the findings, it is demonstrated for the first time that the improved gliding performance when wearing full body swimsuits is linked to changes in swimmers’ morphology due to compression. Study 4. In the fourth study the magnitude of resistive forces applied on a swimmer’s body when gliding underwater was assessed with the use of computational fluid dynamics (CFD) and the LES approach. The results showed a close match between the glide factor values of the experimental and the computational findings demonstrating the effectiveness of the CFD method when the LES approach is employed.