Day beacons are indicated by small _________________________.

Day beacons are used to aid navigation during daylight hours and are typically indicated by small markers. These markers are designed to be visible in daylight and provide important information to boaters, such as indicating safe passage through channels or identifying hazards. They often have distinctive colors and shapes to convey specific meanings about the waterway, helping to guide vessels safely.

The other options do not accurately represent the primary purpose of day beacons. Light signals are used for navigation primarily at night, reflective surfaces are not a standard characteristic of day beacons, and flags may communicate specific signals but are not a standard representation of day beacons themselves.