Drop
If the boomer plate has an old elastic membrane the signal could have a low frequency drop after the first pick.
DC Effect
If the boomer system hasn't a perfect ground the electric noise degrades strongly the signal with a strong DC.
Algae
The vegetation presence on the bottom doesn't permit signal transmission.
Sea waves
If the acquisition is carried out when the sea has some rough waves, data are degradated. During processing it's possible to improve the reflections continuity.
In figure an example of wave correction.
Gassy sediments
The gas presence into the sediments doesn't permit signal transmission.
In
figure you can see gas plumes that hide reflectors.
Ripple signal
Sometimes you have ripple signal if your acquisition geometry. With a deconvolution you could improve your section.
In figure an example of
deconvolution correction.
Note: All these seismic data collected and processed by luca baradello in OGS