At a brief glance, the 13 mutual members of the International Group of P&I Clubs would appear to show a group of marine insurers that all have remarkably similar business models.

But there is one club that stands out as uniquely different and, for the moment at least, appears to be dodging the difficulties that are blighting its rivals.

While many of the P&I mutuals are struggling with underwriting losses in the tens of millions of dollars, the Shipowners' Club kept its underwriting deficit to $900,000 in the first half of...