Neptune Insurance Holdings Inc. shares jumped 24% after the flood insurance company’s shareholders raised $368.4 million in a US initial public offering.Shares of the St. Petersburg, Florida-based firm closed at$24.80 each on Wednesday, versus an IPO price of $20 apiece. The offering of 18.4 million shares by backers including co-founder Jim Albert, Bregal Sagemount and FTV Capital was marketed in a range of$18 to $20 each. The trading gives Neptune a market value of around$3.4 billion based on the outst ...