Complex sentence: When the maneuverability of the berthing vessel is not really high it is often less dangerous for her to approach a vessel stopped in the water so that there will be a protected side from the waves and wind and there will also not be any bow wave.
Split into simpler sentences: When the maneuverability of the berthing vessel is not really high it is often less dangerous for her to approach a vessel stopped in the water. Like that there will be a protected side from the waves and the wind and there will also not be any bow wave.