In this work, we highlight bio-based and biodegradable polyester blends from poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and poly(hydroxybutyrate) (PHB), which are promising materials for additive manufacturing and are a sustainable alternative to petroleum-based plastics. The anisotropy effect of polyesters is widely reported in the literature, while durability issues on 3D printed products are rarely reported. The dog-bone-shaped printed samples were prepared using a fused filament fabrication (FFF) technique, i.e. material extrusion method, and immersed in artificial seawater for six months to assess the polyester material durability under the seawater environments. The blend design is based on a combination of high elastic modulus glassy polymer (PHB and PLA) with ductile PBS. Four biopolyester blends of PBS/PLA and PBS/PHB with ratios 50/50 and 70/30 were melt-processed to create filaments. Scanning electron microscopy (SEM) images demonstrated that the obtained filament showed excellent processability and printability. However, after exposure to seawater ageing, the mechanical performance of the proposed bioplastic blends decreased due to plasticization and chain hydrolysis. The highest decline in mechanical properties demonstrates PBS/PHB 50/50, for which tensile strength and elastic modulus decreased by 3.3- and 2.5-fold, respectively. Differential scanning calorimetry (DSC) analysis revealed that the crystallization temperature of PBS/PHB and PBS/PLA shifted to lower temperatures. In addition, samples with concentric infill exhibit higher water absorption compared to rectilinear infill. The printed bioplastics are suitable for short-term maritime uses, though their long-term durability raises concerns.