A tidal turbine design needs to consider the harsh environment of the sea. Reducing the number of moving parts is therefore desirable. A tidal stream is relatively predictable with small directional variance. To avoid a yaw gear an attractive option is to instead use a reversible airfoil, allowing the turbine to operate in both ebb and tide. This work investigates various reversible airfoil designs and airfoil optimization. The airfoils are based on existing NACA 6 profiles and profiles using B-spline parameterization. The optimization process showed that it is challenging to obtain a profile that has both good lift and good aerodynamic effectiveness as these two parameters are opposing each other. Still, a viable design is obtained that has improved performance compared to the simpler design based on modifying a NACA 6 profile.