The effect of gravitational lensing, traditionally seen with light, is also expected to be observed with gravitational waves. Although gravitationally lensed gravitational waves have not been detected yet, a lensed gravitational-wave event is expected to be detected at any moment. Observing a lensed gravitational wave could be interesting to learn more about the nature and the properties of the lens. In this presentation, we will discuss how lensed gravitational-wave events can be modelled. In particular, how wave effects such as interference and diffraction around the lens affect the signal, giving rise to characteristic features. Accurately modelling the form of gravitational waves is particularly important for gravitational wave searches. To be certain about the detection of a lensed signal, it is necessary to know how much it deviates from other models. We will discuss how the deviations depend on the lensing parameters and the implications for searches.