I tested it out with some LADS data I have from Portsmouth Harbor. You can see the selected data points highlighted in yellow in the plan view. The point highlighted in blue is the current "super-selected" point, and it is for this data point that CARIS will display the waveform. If you click either "next" or "previous" in the lefthand lidar menu, the "super-selected" point will move to the next yellow highlighted point and you can view the waveforms for each of the selected soundings.
The waveform box shows the surface and bottom returns for the green waveform. The green line represents the detected bottom depth for the waveform, while the red line represents a possible alternate depth. Unfortunately, there is no way to display axes (neither time nor intensity) or any type of scale on the waveform in order to get a better sense of what is being displayed. This is something CARIS will hopefully correct in later versions or hotfixes.