Over the past decades, there has been a growing interest in biologically inspired robots, artificial micro- and nano-machines, driven by their use in several fields such as microfluidics, particle manipulation and materials assembly. More recently, an increasing excitement has surrounded their potential applications in targeted drug delivery, minimally-invasive diagnostic and microsurgery. Progress has already been made in the development of artificial microswimmers employing different actuation methods, including chemical reactions, diffusion-driven mechanisms and self thermophoresis. We focus on the concept of the BioBot, a muscular-driven swimmer integrating biological tissues for its functional capabilities and artificial activation devices. In particular we develop a new class of swimmers by selecting an appropriate structural design, system kinematics and fluid-structure interaction. Fluid mechanics principles are then used to identify the optimal swimmer and the relevant characteristics that affect dynamic performance. Our state-of-the-art numerical tool allows us to accurately design, simulate and optimise the muscle structure by means of direct numerical simulations, i.e. without introducing any turbulence model or fluid approximation. Our results show very robust features that make the proposed proof-of-concept design suitable for real-world applications.