The world's biggest dredger lifted net profit to $158.6 million in the six months to June 30 from $131.5 million in the year-earlier period as revenue advanced to $1.45 billion from $1.26 billion.
The takeover of Rotterdam-based Smit International, which took effect in the second quarter, contributed $205 million of revenue and a $12.2 million profit.
Boskalis paid $1.7 billion for Smit, one of the world's biggest marine salvage companies, which is also active in harbor towage, heavy lift shipping and cargo terminals.
"We have had a very strong first half year with a particularly good performance within the core dredging activities," said Boskalis CEO Peter Berdowski.
"Thanks to the well-filled and broadly spread order backlog we had at the start of the year, we had solid utilization rates for our vessels and realized fine margins on these projects."
Boskalis said it now expects 2010 profit to increase 10 to 15 percent from last year having forecast in May that earnings would be below the 2009 level.
"However, in the current market we are seeing reluctance with clients causing a decline in the volume of work as well as further pricing pressure," Berdowski cautioned.
Dredging was "particularly strong" through the first half although the short term outlook for infrastructure projects has become considerably less certain since the start of 2009 due to the fall in oil prices and uncertainty over demand for raw materials.
The harbor towage and terminal units benefited from a gradual recovery in port traffic but heavy lift shipping contract rates fell on fewer oil and gas contracts.