Undersea oil contractor Acergy is to acquire rival Subsea 7 in an all-share deal for an estimated $3.4bn.
In a joint statement, the companies said the $5.4bn combined entity will create a global leader in seabed-to-surface engineering and construction.
The companies expect annual synergies of at least $100m and have an order backlog of $5.3bn.
The all-share deal is based on the market value of both companies, with Acergy owning 54% of the new entity and Subsea 7 holding the remaining 46%.
The merger is expected to be completed towards the end of this year or the first quarter of 2011.