acceptible profession for the younger sons of gentlemen... and people who were on the cusp of gentility and had been for a long time. Makign money from Prize money was not new. it was just that the long wars with France had given sailors a chance to make fortunes in greater numbers than previously. Its not as if Anne were marrying soemone whose money was made in trade. Lady R doesn't think well of Fred becuase alhthough he's a gentlemen he's from a not very well off family, his father is merely a clergyman without much money... and mainly becauase he's also not well off himself and while he has made some moeny is in her opinion over confident about the idea that he will go on being lucky and make his fortune...