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This paper describes an optimization study of a spherical composite submersible pressure hull employing a genetic algorithm (GA) in ANSYS. A total of five lay-up arrangements were optimized for three unidirectional composites carbon/epoxy, glass/epoxy, and boron/epoxy. The minimization of the buoyancy factor <inline-formula> <math display="inline"> <semantics> <mrow> <mrow> <mo>(</mo> <mrow> <mi>B</mi> <mo>.</mo> <mi>F</mi> </mrow> <mo>)</mo> </mrow> </mrow> </semantics> </math> </inline-formula> was selected as the design optimization objective. The Tsai-Wu and Tsai-Hill failure criteria and buckling strength factor <inline-formula> <math display="inline"> <semantics> <mrow> <mrow> <mo>(</mo> <mi>λ</mi> <mo>)</mo> </mrow> </mrow> </semantics> </math> </inline-formula> were used as the material failure and instability constraints. To determine the effect of geometric non-linearity and imperfections on the optimized design, a non-linear buckling analysis was also carried out for one selected optimized design in ABAQUS. The non-linear buckling analysis was carried out using the modified RIKS procedure, in which the imperfection size changed from 1 to 10 mm. A maximum decrease of 65.937% in buoyancy factor <inline-formula> <math display="inline"> <semantics> <mrow> <mrow> <mo>(</mo> <mrow> <mi>B</mi> <mo>.</mo> <mi>F</mi> </mrow> <mo>)</mo> </mrow> </mrow> </semantics> </math> </inline-formula> over an equivalent spherical steel pressure hull was computed for carbon/epoxy. Moreover, carbon/epoxy displayed larger decreases in buoyancy factor <inline-formula> <math display="inline"> <semantics> <mrow> <mrow> <mo>(</mo> <mrow> <mi>B</mi> <mo>.</mo> <mi>F</mi> </mrow> <mo>)</mo> </mrow> </mrow> </semantics> </math> </inline-formula> in the case of 4 out of a total of 5 lay-up arrangements. The collapse depth decreased from 517.95 m to 412.596 m for a 5 mm lowest mode imperfection. Similarly, the collapse depth decreased from 522.39 m to 315.6018 for a 5 mm worst mode imperfection.