49 CFR § 831.51 - Definitions.
The following definitions apply throughout this subpart.
IIC means the NTSB investigator-in-charge.
Investigative activity means an activity performed by or under the direction of the NTSB during a casualty investigation led by the USCG.
Marine casualty means -
(1) Any casualty, accident or event described in 46 CFR 4.03-1
(2) An occurrence that results in an abandonment of a vessel
(3) Other marine occurrences that the NTSB or USCG, or both, determine require investigation.