Myotis macropus MYMA
Steep call without any clear start or end but with a energy maximum around 40 kHz. Note the echo cloud in the spectrogram.
In search phase there is often a clear S-form that straightens out when the bat enters a more active phase. Here are two details from the spectrogram above showing that.
Here is another feeding sequence:
When the bat gets closer to the water surface, there will be interference between the direct and the reflected wave. Here is the impact on the oscillogram and the spectrogram.