Close Call With Manned Aircraft

[B52-D]

Well...probably. Here is the relevant passage regarding minimum safe altitudes for aircraft. Emphasis is mine

91.119 Minimum safe altitudes; general

(c) Over other than congested areas – An altitude of 500 feet above the surface except over open water or sparsely populated areas. In that case, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.

So by that definition, the dock and you were closer than 500'...most likely.

However...look at (d)

Helicopters – Helicopters may be operated at less than the minimums prescribed In paragraph (b) or (c) of this section if the operation is conducted without hazard to persons or property on the surface. In addition, each person operating a helicopter shall comply with routes or altitudes specifically prescribed for helicopters by the Administrator.

What I don't know, is if the FAA considers a gyroplane a fixed wing aircraft or a helicopter. My GUESS is it's in the plane column, but i don't know that for sure. Either way, I think the pilot was not being responsible.
That said, if this area is known for lots of flying things, then perhaps flying in a different location would be prudent.

Lastly...

For more information, or to report a low-flying aircraft, please contact your local FSDO. For a list of FSDO’s pertaining to your area, click here.

By FAA Definitions I don’t believe it’s a plane (aircraft)

Title 14 → Chapter I → Subchapter A → Part 1 → §1.1
Airplane means an engine-driven fixed-wing aircraft heavier than air, that is supported in flight by the dynamic reaction of the air against its wings.

Helicopter means a rotorcraft that, for its horizontal motion, depends principally on its engine-driven rotors.

Rotorcraft means a heavier-than-air aircraft that depends principally for its support in flight on the lift generated by one or more rotors.

e-CFR data is current as of January 7, 2021

Title 14 → Chapter I → Subchapter A → Part 1 → §1.1

Title 14: Aeronautics and Space

PART 1—DEFINITIONS AND ABBREVIATIONS

Gyroplane means a rotorcraft whose rotors are not engine-driven, except for initial starting, but are made to rotate by action of the air when the rotorcraft is moving; and whose means of propulsion, consisting usually of conventional propellers, is independent of the rotor system.

Blue Skys & Happy Trails

 

[spamgnome]

PART 1—DEFINITIONS AND ABBREVIATIONS

Gyroplane means a rotorcraft whose rotors are not engine-driven, except for initial starting, but are made to rotate by action of the air when the rotorcraft is moving; and whose means of propulsion, consisting usually of conventional propellers, is independent of the rotor system.

Blue Skys & Happy Trails

Thanks for finding that...so as it pertains to the minimum altitude rules, which is a gyroplane governed by? I would think airplane, because the flight characteristics more closely resemble an airplane. For example, a gyroplane cannot take off and land vertically.