46 C.F.R. § 44.01-1
Establishment of load lines for special services
(a) Load lines are established for steam colliers, tugs, barges, and self-propelled barges engaged in special services in conformity with regulations in this part.
(b) Load lines for steam colliers, barges, and self-propelled barges engaged on specially limited coastwise voyages as described in § 44.01-12 shall be established pursuant to the regulations in this part.
(c) Variance for tugs is not permitted.