Here's the list straight from the CFR's. Note "Include" doesn't limit to these choices:
Y valve lockouts
(b) When operating a vessel on a body of water where the discharge
of treated or untreated sewage is prohibited by the Environmental
Protection Agency under 40 CFR 140.3 or 140.4, the operator must secure
each Type I or Type II device in a manner which prevents discharge of
treated or untreated sewage. Acceptable methods of securing the device
include--
(1) Closing the seacock and removing the handle;
(2) Padlocking the seacock in the closed position;
(3) Using a non-releasable wire-tie to hold the seacock in the
closed position; or
(4) Locking the door to the space enclosing the toilets with a
padlock or door handle key lock.
(c) When operating a vessel on a body of water where the discharge
of untreated sewage is prohibited by the Environmental Protection Agency
under 40 CFR 140.3, the operator must secure each Type III device in a
manner which prevents discharge of sewage. Acceptable methods of
securing the device include--
(1) Closing each valve leading to an overboard discharge and
removing the handle;
(2) Padlocking each valve leading to an overboard discharge in the
closed position; or
(3) Using a non-releasable wire-tie to hold each valve leading to an
overboard discharge in the closed position.
[CGH 95-028, 62 FR 51194, Sept. 30, 1997]