Since I do not know that particular recording (- it is not on YouTube), I cannot possibly say whether your key is the same as theirs. Worse still, the tune goes around in many variants. The one stored in the MIDI file of the DT seems a bit questionable to me, first of all because it suggests a chorus of four lines. Anyway, it does not seem to be the version you are using.

Our chanty experts are likely to appear soon, presumably to remind us that for utmost authenticity, such songs should not be accompanied at all. If they want to do us more of a service, they may provide "authoritative" versions of the tune in ABC format, preferably with "w:" lyrics of the first stanza. Thanks in advance! We can then discuss about chords for those who want any.