Ballsy control operator

Can someone tell me what type of license this paragraph refers to.
46 CFR 11.474 paragraph (b)
An applicant for an endorsement as bco who holds an unlimited license or MMC endorsement as master, mate, chief engineer, or assistant engineer must satisfy the requirements in paragraph (a) (2) of this section and have at least 28 days of service as a trainee under the supervision of an individual holding an endorsement as ballast control operator.

Haha auto correct on the I phone I meant ballast control operator

I’d love a license as ballsy control operator…

Drilling rigs carry ballast control operators. Rigs that require deck licenses will have their mates get bco, usually their engineers as well.