The latter is the current head of corporate finance at the group and has been with Atlantis since before its IPO (initial public offering) in 2014.
"I would like to thank Simon for his support and hard work over the last two years as we have transitioned the finance department from Singapore to Edinburgh, where he has built a highly competent team," said Atlantis chief executive Tim Cornelius.
"I am delighted that Andrew will have the opportunity to join the operations board as CFO. Andrew joined Atlantis in 2014 and has been an integral part of the team since then. He worked on the IPO, the acquisition of Marine Current Turbines from Siemens AG and the financial close of MeyGen Phase 1A. He brings a wealth of experience in global renewable energy generation and we all look forward to working with him as we continue to build on Atlantis's successes."
Last week the group said it had now closed its £5mln ‘green’ bond, with full subscription.
Together with its recent £4.1mln share placing the company intends to use the new capital to grow the business, repay its more expensive debt and for working capital purposes.
It also noted that it is no longer in talks with a potential strategic investor which, in May, was said to be interested in taking a stake in the company.
Shares were unchanged at 38p.