The acquisitions, to be funded by a $30 million institutional share placement, are subject to shareholder approval.

Neptune managing director Christian Lange said Tri-Surv and USUS would accelerate his company’s growth strategy.

“Tri-Surv and USUS will give Neptune greater critical mass, an expanded geographical footprint and lay the foundation for Neptune to become a leading international subsea engineering and integrated services provider,” Lange said.

“The worldwide subsea oil and gas services market is expected to grow significantly, supported by the development of new, more complex deepwater oil and gas fields and the ongoing maintenance of existing ageing infrastructure.

“Our immediate objective is to complete the transactions, integrate the businesses and continue to grow our operations in Australia and internationally. Neptune now has the scale and capability to migrate a totally integrated subsea engineering and services model into large oil and gas markets and this is now a priority.”

Tri-Surv is a specialist hydrographic surveying company based in Perth with customers in Western Australia and New Zealand.

Neptune has signed a letter of intent, proposing to pay $16.7 million upfront in 70% cash and 30% Neptune shares, plus a three-year earn-out based on Tri-Surv’s pre-tax earnings performance.

The acquisition is subject to due diligence, contractual documentation and completion of a share placement.

USUS is a commercial diving contractor based in Texas and operating mainly in the Gulf of Mexico.

The purchase price is about $26.3 million, including $7 million of assumed debt, a multiple of 5.5 times estimated 2007 earnings before tax, depreciation and amortisation.

Since mid-2006, Neptune has take over four Australian companies – Subsea Developments, Link Weld, Allied Diving Services and Territory Diving Services.