Catastrophes involving mass movements has always been a great threat to civilizations. We propse to simplify the behavior of the mass movement material as a highly viscous fluid, possibly non-Newtonian. In this context, this study describes the application of two improvements in highly viscous fluid simulations using the smoothed particle hydrodynamics (SPH) method: an implicit time integration scheme to overcome the problem of impractically small time-step restriction, and the introduction of air ghost particles to fix problems regarding the free-surface treatment. The application of a fully implicit time integration method implies an adaptation of the wall boundary condition, which is also covered in this study. Furthermore, the proposed wall boundary condition allows for different slip conditions, which is usually difficult to adopt in SPH. To solve a persistent problem on the SPH method of unstable pressure distributions, we adopted the incompressible SPH  as a basis for the implementation of these improvements, which guarantees stable and accurate pressure distribution. We conducted non-Newtonian pipe flow simulations to verify the method and a variety of dam break and wave generated by underwater landslide simulations for validation. Finally, we demonstrate the potential of this method with the highly viscous vertical jet flow over a horizontal plate test, which features a complex viscous coiling behavior.