Cal Dive International Inc., Houston, (NYSE: DVR) plans to acquire Horizon Offshore Inc., Houston, (Nasdaq: HOFF) for $650 million in cash, stock and assumed debt. Horizon's fleet consists of nine vessels that provide marine construction services primarily to offshore energy companies in the U.S. Gulf of Mexico, Latin America, southeastern Asia, the Mediterranean and West Africa. The combined company will operate a fleet of 23 diving-support vessels, seven pipelay/pipebury barges, one dedicated pipebury barge, one multi-service vessel, one combination derrick/pipelay barge and two derrick barges. The assets will expand Cal Dive's geographic footprint, enhance international growth opportunities and further diversify operations.