Wave energy is currently an untapped resource, but has the potential to make a significant contribution to the energy mix. In order to use conventional electrical generators mechanical interfaces are used, such as hydraulic systems and air-turbines. With the electrical generator these interfaces are known as the electrical power take-off and the type used depends upon the wave energy device. A brief description of the different power take offs is provided to show how conventional rotary generators are used in wave devices. Both advantages and disadvantages are highlighted in the paper. Direct drive systems can overcome some of the disadvantages, but there are additional engineering challenges to overcome, in particular physical size and mass. Current and more novel direct machine topologies are discussed in the context of these challenges.