As has been pointed out, the cable loss (within reason), is a somewhat moot point.

Given an antenna height of X, it is not hard to calculate the maximum expected range, plus some for
refraction, then also given the typical receiver sensitivity, (assume 10 microvolts for a
not-so-good receiver), and antenna gain, you'll find that the power required at the antenna is not
much. When the boat's rock and roll effect on the antenna pattern is considered, the power
requirements of course must go up. As a side note: low gain antennas are better in this respect,
assuming the low gain is due to an wider vertical beam-width, and not just poor design.

But in my estimation, the real key to reliable marine VHFcommunications is in the connectors.

When a young lad I spent 5 years maintaining antennas (all frequencies) in a coastal environment,
(actually, within 200 yards of the beach) and can assure you that an unprotected/exposed connector
in salt air can bring an antenna to its knees in 3 to 6 months.

Norm