SeaBright Holdings, which sells workers-compensation insurance to maritime employers and other niche markets, is sailing off into the sunset.

The Seattle-based specialty insurer said late Monday it is being acquired by Enstar Group of Bermuda for $252 million, or $11.11 a share. That’s 34.3 percent above Monday’s closing price of $8.27 a share.

The two companies said they expect the deal to close in the first quarter of 2013.

Enstar specializes in acquiring insurance and reinsurance companies in “run-off” mode — that is, managing existing assets and paying claims but not writing any new policies.

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SeaBright, which traces its roots to the Eagle Pacific Insurance division of Services Group of America, went public in January 2005 at $10.50 a share after a series of ownership changes.

While its assets have nearly quintupled since then to $1.1 billion, its core business has struggled in recent years. The company posted net losses in 2010 and 2011, though it reported a $9.5 million profit for this year’s first six months.

The stock peaked in mid-2007 at $19.74, and has been ratcheting lower ever since.

Drew DeSilver: 206-464-3145 or ddesilver@seattletimes.com