First many waterfront locations have restrictions. You can find out what they are in your local jurisdiction. And some have different restrictions at different times of year.
So, let us think of the number of guests, time of year, time of day and the surrounding elements.
It is a nice sunny hot summer Saturday and it is your wedding day. You may want an earlier ceremony time before your surroundings get crowed. They can make for noise and people walking behind the couple as the photographer is trying to capture the two of you.
What if it rains? Many locations for waterfront smaller set up can be on hold for an hour or so, earlier, or later. It is important to let your guest know this potential time change. This last minute change is much easier for smaller intimate ceremonies.