National vs International water AB

What is the difference between National AB and International STCW able seafarer deck? I have National AB special, Lifeboatman, STCW basic. I plan on working on tugs SoCal. Assuming its distance offshore, is it 3, 12, or 200 NM? Is it the separation of inland waters and near coastal? Are these endorsements capable of climbing the hawsepipe with? Thanks

It isn’t the distance offshore that matters. If the tug is under 200 GRT the difference is whether or not it is on a domestic voyage or an international one.

Subpart K—Vessels Subject to Requirements of STCW
USCG-2004-17914, 78 FR 78010, Dec. 24, 2013, unless otherwise noted.
§ 15.1101General.
(a) Except as noted in paragraphs (a)(1) and (2) of this section, the regulations in this subpart apply to seagoing vessels as defined in § 10.107 of this subchapter.
(1) The following vessels are exempt from application of the STCW Convention:
(i) Fishing vessels as defined in 46 U.S.C. 2101(11)(a).
(ii) Fishing vessels used as fish-tender vessels as defined in 46 U.S.C. 2101(11)(c).
(iii) Barges as defined in 46 U.S.C. 102, including non-self-propelled MODUs.
(iv) Vessels operating exclusively on the Great Lakes or on the inland waters of the U.S., in the Straits of Juan de Fuca, or on the Inside Passage between Puget Sound and Cape Spencer.
(v) Pilot vessels engaged on pilotage duty.
(2) The following small vessels engaged exclusively on domestic voyages are not subject to any obligation for the purposes of the STCW Convention:
(i) Small passenger vessels subject to subchapter T or K of 46 CFR chapter I.
(ii) Vessels of less than 200 GRT (other than passenger vessels subject to subchapter H of 46 CFR chapter I).
(iii) Uninspected passenger vessels as defined in 46 U.S.C. 2101(42)(B).
(b) Masters, mates, and engineers serving on vessels identified in paragraphs (a)(2)(i) and (a)(2)(ii) of this section may be issued, without additional proof of qualification, an appropriate STCW endorsement when the Coast Guard determines that such a document is necessary to enable the vessel to engage on a single international voyage of a non-routine nature. The STCW endorsement will be expressly limited to service on the vessel or the class of vessels and will not establish qualification for any other purpose.

So let me get this straight. If a tug or a vessel under 200 grt travels from say long beach to San Diego, CA you can get by with a national endorsement. But if you take the vessel down to a port in a foreign country you need stcw able seafarer?

Yes. See 46 CFR 15.1103(c). Note that for these purposes, 200 GRT is assumed to be equivalent to 500 GT. See also the definition of “seagoing vessel” in 46 CFR 10.107.