Coast Guard – This email address is a confidential one for reporting any suspicious activity or concerns: [email protected] (also copy [email protected]). There is some concern this may no longer be in use. 

Call at any time on VHF channels 16, 13, 11.
Between Cartagena and Panama there are Coast Guard stations at Islas del Rosario, Coveñas (which covers both Islas San Bernardo and Isla Fuerte), and Turbo in the Gulf of Urabá (which covers Zapsurro Bay).

There are significant gaps in the coverage of VHF along the coast, although the fixed stations are supplemented by Coast Guard units that are constantly on patrol.