How rare were 104-gun first rates?

How many 104-gun ships of the line would have been operating in the Caribbean during the 1710s and 1720s?

Very few; the Royal Navy had only about six or seven first rates in total, not fleets of them roaming the Caribbean.

A 104-gun ship of the line was a first rate. The estimate given here is only about six or seven first rates across the Royal Navy, with roughly the same number of second rates, and even those figures may not fit every year in the 1710s and 1720s. A game that repeatedly places such ships in the Caribbean therefore exaggerates their availability. The Royal Navy tended to prefer first and third rates, and its dislike of second rates is linked here to the later disparaging phrase.