The ship's master is responsible for the health of persons aboard Dutch seagoing vessels. 
In practice, however, medical duties are usually delegated to the first mate.

Limited Medical Training-L Certificate
Aboard Dutch vessels operating in a sailing area A1/A2, the master and (if applicable) the officer responsible for medical treatment must hold the Limited Medical Training-L Certificate.

Limited Medical Training-L Certificate for near coastal waters
Aboard Dutch vessels with a sailing area limited to the GMDSS Sea Area A1, up to 30 miles from the coast of a European country, the master and (if applicable) the officer responsible for medical treatment must hold the Limited Medical Training-L Certificate for near coastal waters.

Unlimited Medical Training-U Certificate
Aboard Dutch vessels operating in an unlimited sailing area A1/A2/A3/A4, the master and (if applicable) the officer responsible for medical treatment must hold the Unlimited Medical Training-U Certificate.