Permission needed
1. What the city publishes
A Metal Detector Permit is required for individuals who wish to use metal detectors in Baltimore City Parks. … Applicants must be at least 16 years old and present a government-issued photo ID. Completion of a training session from a recognized metal detecting club is mandatory. A $25 fee (payable via Money Order or Credit/Debit Card) is required for issuance and yearly renewal. … Digging deeper than 8 inches is prohibited, and all holes must be properly restored. Certain locations, including Carroll Park, Federal Hill Park, and the Inner Harbor, are off-limits. Metal detecting is prohibited in July and August each year.
2. The state rule also applies
Designated swimming beaches only, for modern coins and jewellery, with Point Lookout and Calvert Cliffs excluded – and not between 9am and dusk from late May to Labor Day.
3. County rules
Awaiting review.