I wouldn't run beach mode. If you are looking primarily for coins or deep targets, run Park 1, for relics then Park 2 or Field 2. Run sensitivity as high as you can without chatter. Do a noise cancel and GB at the beginning and swing away. On dry sand at beaches, I go with the deepest stable mode I can get away with, not necessarily Beach 1. That might mean going with gold mode if I am trying to target micro gold jewelry and can get it to run stable.
Beach modes are set up to run stable in salt beach conditions. Because of this, certain compromises are made such as the inability to run single frequency if desired and in the case of Beach 2, transmit power can be automatically throttled back if mineralization is detected. Most folks do not run beach mode at freshwater beaches for this reason. Beach modes should be used only if you are forced to go there to keep the machine stable in moderate to high salinity conditions. Beach 1 is less "compromised" than Beach 2, but why run eitger if you can get away with running more capable modes in a stanle manner.