The concept of wireless power is originated from Heinrich Hertz and well known by the work of Nikola Tesla. Magnetic resonance-based wireless power transfer has been widely applied in charging biomedical implants, consumer electronics, electric vehicles, and lightweight autonomous underwater vehicles due to its convenience and reliability. As a core part of a wireless charging system, coil design is of great importance. This dissertation will introduce four coil designs based on the applications of wirelessly charging electric vehicles and lightweight autonomous underwater vehicles. Chapter 2 proposes an integrated coil design for bipolar coils in EV wireless chargers using LCC compensation topology, which simplifies the design, makes the system more compact, and increases the system power density. Finite element analysis by ANSYS MAXWELL is conducted to verify the proposed idea. In addition, a design method on improving system efficiency is given and experimental results demonstrate that wireless charging system with the proposed integrated coil design can transfer 3.0 kW at a DC-DC efficiency of 95.5%. Chapter 3 extends the work of Chapter 2 and presents another integrated coil design which is compatible with unipolar coils in EV wireless chargers using LCC compensation topology. The aspect ratios of the compensated coils are study in ANSYS MAXWELL to minimize the extra cross-side coupling coefficient. A wireless charging with the proposed integrated coil design is built to achieve 3.0 kW power transfer at a DC-DC efficiency of 95.5%. Furthermore, a comparative study of the two wireless charging systems in Chapters 2 and 3 are conducted, and the results show the wireless charging system in Chapter 3 has competitive performance in fully aligned and door-to-door misaligned cases, and superior performance in vertical and front-to-rear misaligned cases. Chapter 4 puts forward a three phase coil design for lightweight autonomous underwater vehicles. Finite element analysis shows the proposed coil structure has concentrated magnetic fields, which have less adverse effects on the instrumentations within the AUV. A compensation method is presented and a three-phase wireless charging system is built to transfer 1.0 kW at a DC-DC efficiency of 92.41%. Chapter 5 proposes a rotation-resilient coil design with a two-part reversely wound receiver for lightweight autonomous underwater vehicles in order to achieve a constant power transfer over rotational misalignment. Finite element analysis is performed to verify the proposed coil design and a mesh-current method is applied in analyzing the circuit. A wireless charging system is built to deliver 745 W at a DC-DC efficiency of 86.19% when the system is fully aligned, and efficient under worst-case rotational misalignment.