I usually suggest having your 20-30 minute ceremony end about an hour before sunset. That means starting your ceremony about an hour and a half before sunset.
This approach will leave ample time with proper sunlight for your beach wedding pictures. It also supplies a much needed buffer zone for wardrobe malfunctions, bridge openings, and unanticipated traffic.
Consider the sun when planning your wedding. Make sure to check sunrise and sunset times for your wedding day.