[Airwaves]

You will need to get a permit from the state prior to setting out a swim line:

270:26 Injuring Buoys, Placing Obstructions. –
I. Any person who knowingly removes, destroys, moves, or injures any buoy, beacon, or other navigational aid placed in, on, or adjacent to any of the public waters of the state for the purpose of guiding and protecting navigation and boating thereon shall be guilty of a misdemeanor.
II. Any person who knowingly places an obstruction dangerous to navigation in any of the public waters of the state without reasonable precaution to protect the public from such obstruction shall be guilty of a misdemeanor.
III. Any person who shall moor or make fast a boat, vessel, raft, or float of any description to a buoy, beacon, or other navigational aid placed in, on, or adjacent to the public waters of the state shall be guilty of a violation.
IV. (a) Any person who knowingly places a swim line in any public body of water without first obtaining a permit issued by the director of safety services shall be guilty of a violation.
(b) Any person who operates a boat within any permitted swim line on any public body of water without the permission of the permittee shall be guilty of a violation.
(c) The commissioner is authorized to establish fees and expiration periods for permits issued under subparagraph (a). The fee for a permit shall not be greater than $50 and all permits shall expire no later than 5 years after the date of issuance. All fees collected under this paragraph shall be deposited in the navigation safety fund established under RSA 270-E:6-a.