33 CFR §161.18

1. (a)A Center may: (1) Direct a vessel to provide any of the information set forth in Table 161.18(a) (IMO Standard Ship Reporting System);
   1. (2)Establish other means of reporting for those vessels unable to report on the designated frequency; or
   2. (3)Require reports from a vessel in sufficient time to allow advance vessel traffic planning.
2. (b)All reports required by this part shall be made as soon as is practicable on the frequency designated in Table 161.12(c) (VTS and VMRS Centers, Call Signs/MMSI, Designated Frequencies, and Monitoring Areas).
3. (c)When not exchanging communications, a VMRS User must maintain a listening watch as described in § 26.04(e) of this chapter on the frequency designated in Table 161.12(c) (VTS and VMRS Centers, Call Signs/MMSI, Designated Frequencies, and Monitoring Areas). In addition, the VMRS User must respond promptly when hailed and communicate in the English language.
4. (d)A vessel must report:
   1. (1)Any significant deviation from its Sailing Plan, as defined in § 161.19, or from previously reported information; or
   2. (2)Any intention to deviate from a VTS issued measure or vessel traffic routing system.
5. (e)When reports required by this part include time information, such information shall be given using the local time zone in effect and the 24-hour military clock system.