The beach is usually bright light and light colored sand that will fool your camera into underexposing the film. Set your exposure compensation if the camera has it to +1 or +2 and try some shots. If the camera has no compensation dial then set your ASA dial to half the rated film speed to get more exposure. Try a few and see if it works the way you want it to, if the negatives are still too underexposed set the ASA dial lower.
Do this for those high key shots (a lot of light tones) and set it back to normal for pictures with a full range of tones so you don't have errors the other way.