According to the Ministry of Transport & Infrastructure Development, captains of vessels must be Zimbabwean nationals because there are adequate personnel in the market. This is applied according to the relevant provisions in the Immigration Act and its implementing rules. [The OECD, however, could not identify any specific subsidiary regulation on this specific matter, i.e. nationality of masters of vessels].
"19 Refusal to issue residence permit
(1) The Minister may direct that a residence permit shall not be issued by the Chief Immigration Officer to any particular person or to a member of a class of persons.
(2) The Chief Immigration Officer—
(a) shall, if the applicant is a person or a member of a class of persons in respect of whom the Minister has given a direction in terms of subsection (1), refuse to issue a residence permit to the applicant;
(b) may, if the applicant is not a person referred to in paragraph (a), for any reason refuse to issue a residence permit to the applicant.
(3) Any person whose application for a residence permit has been refused in terms of paragraph (b) of subsection (2) may, if he is able to produce fresh evidence relating to the application or to show that the circumstances affecting his case have changed, within 14 days of being notified of such refusal, make representations to the Chief Immigration Officer and the Chief Immigration Officer shall, subject to subsection (2), reconsider the application.
(4) No person whose application for a residence permit has been refused—
(a) in terms of paragraph (a) of subsection (2) shall be entitled to be given any information or reasons for the direction of the Minister referred to in that paragraph; or
(b) in terms of paragraph (b) of subsection (2) shall be entitled to be given any information or reasons as the grounds for such refusal.
(5) Notwithstanding any provisions of these regulations, the Minister may in any particular case direct that a residence permit shall be issued to any person and the Chief Immigration Officer shall comply with such direction.[...]" (Immigration Regulations, 1998, as amended)
Immigration Regulations, 1998, as amended
[<a href="http://www.zimimmigration.gov.zw/index.php/typography/immigration-regulations">Reg</a>]