Any unbalanced antenna requires a counterpoise. Similar to your handheld radio with a whip, it literally uses your body as a counterpoise. How "elaborate" you want to make it is largely subjective and a matter of personal preference.
I have read some think simply connecting it to a thruhull is sufficient; others recommend a larger counterpoise. Still others use a Dynaplate.
The best advice I can offer is install a minimal one and make ypour own judgment if expansion is needed as all boats effect radiation patterns differently and all owners have different expectations.
Anyone who tells you only one answer is correct in every case should be considered a dubious source.