<p>The design of horizontal storage tanks for offshore platforms and floating wind systems is strongly constrained by wave-induced sloshing, yet systematic guidelines for selecting geometry and internal baffling under multi-degree-of-freedom (DOF) motions are still limited. In this study, we develop a design-oriented hydrodynamic optimization framework for cylindrical and bi-lobed sloshing tanks subjected to pitch, heave, and surge excitations. A staged RANS–VOF CFD program, validated against shake-table experiments, is used to explore fixed-volume cylindrical tanks over aspect ratio, fill ratio, and number of vertical baffles, including variations in baffle submergence. Based on the resulting response maps, we identify near-optimal “stubby” geometries and regime-specific baffling configurations and then construct a volume-matched bi-lobed tank by combining two optimized cylinders. To enable a fair comparison, the cylindrical and bi-lobed configurations are evaluated under the same total liquid volume (and identical prescribed excitation conditions), so that differences in response arise from geometry and internal design rather than volume. Both layouts are benchmarked under single- and multi-DOF excitations over a wide frequency range. The results show that appropriate combinations of tank aspect ratio, fill ratio, and baffling can reduce near-resonant sloshing forces by up to about 90% relative to unbaffled slender baselines and markedly flatten and broaden the response dome. We further demonstrate frequency ranges in which bi-lobed geometries outperform cylindrical tanks, particularly under surge and in pre-resonant conditions. The synthesized design maps provide practical guidelines for choosing tank geometry, fill level, baffle number, and baffle submergence to expand safe operating windows for offshore storage and floating wind applications.</p>