Defense Tech Underground #018
Erik Bethel and Rear Admiral Lorin Selby, USN (Ret.) are General Partners at Mare Liberum, an investment firm dedicated to advancing stability and strategic advantage at sea. The fund invests at the intersection of critical technologies and the maritime domain, backing founders building next-generation maritime capability across autonomous platforms, domain awareness, resilient logistics, and advanced manufacturing.
Bethel is a seasoned global finance professional with over two decades of experience in private equity, venture capital, and investment banking at J.P. Morgan, Morgan Stanley, and Franklin Templeton. Most recently, he was a Partner at Americas Frontier Fund, where he specialized in deep tech and strategic investments. His public sector experience includes serving as the U.S. Representative to the World Bank, where he was unanimously confirmed by the Senate and oversaw the deployment of over $100 billion in capital. In 2020, he was nominated to serve as the U.S. Ambassador to the Republic of Panama. He is a graduate of the United States Naval Academy and the Wharton School.
Admiral Selby is a submarine warfare officer, acquisition professional, and nuclear engineer who served more than 30 years in the U.S. Navy. He retired as the Navy’s 26th Chief of Naval Research, where he led a distributed team of 3,800 personnel and oversaw a $4 billion budget developing leading-edge technologies for the Navy and Marine Corps. Prior assignments include serving as the first non-Engineering Duty Officer selected as the Chief Engineer of the Navy and Deputy Commander, Naval Sea Systems Command. His command at sea was the nuclear fast attack submarine USS GREENEVILLE (SSN 772). He holds a B.S. in Nuclear Engineering from the University of Virginia, and an M.S. in Nuclear Engineering and Nuclear Engineer Degree from MIT.
In this episode of Defense Tech Underground, we sit down with Erik and Admiral Selby to explore why the maritime domain is the most consequential and under-invested theater in great power competition, and why the capital markets are finally ready to do something about it. We cover:
From the Navy to Wall Street to a maritime fund — Erik’s career arc from the Naval Academy through J.P. Morgan, the World Bank, and Americas Frontier Fund, and how each chapter pointed toward the same conclusion: the maritime domain was becoming more important, not less, and dramatically underappreciated by investors.
30 years under the surface — Admiral Selby’s career from commanding a nuclear fast attack submarine to running the Office of Naval Research, and what convinced him the right move after taking off the uniform was to help build a venture fund.
Investment strategy and defining “maritime” — Mare Liberum’s approach to stage, check size, and sector focus, and how they draw the boundaries around a domain that spans autonomous platforms, subsea infrastructure, port security, and supply chain resilience.
The submarine industrial base — where we stand on sub production given backlogs, supplier fragility, and workforce gaps, and where Admiral Selby sees investable opportunities to relieve those bottlenecks.
Rebuilding the maritime industrial base — why the real story is not the platform but the plumbing, and how Mare Liberum thinks about investing in the enabling layer of yards, components, labor, and logistics that make the whole base work again.
Selling to the Navy — the biggest structural challenges startups face in navigating Pentagon procurement, where real progress is being made, and what Mare Liberum does to help portfolio companies engage with the government without losing commercial focus.
SBICCT and the Office of Strategic Capital — how Mare Liberum secured a green light letter from both the SBA and the Pentagon’s Office of Strategic Capital to operate as a Small Business Investment Company Critical Technologies fund, unlocking up to $150 million in low-cost government-guaranteed leverage, and what it signals that the government is co-investing alongside private capital into critical maritime technologies.
What’s next for American sea power — near-term milestones to watch from Mare Liberum, specific capability areas they are hunting, and what success looks like in five years if the fund works as intended.
This conversation highlights how a Naval Academy graduate turned global financier and a retired Chief of Naval Research are combining decades of maritime expertise with venture capital to rebuild American dominance at sea.
This episode is hosted by Andrew Couillard and Nate Low
Full Bio: Erik Bethel
Erik Bethel is a General Partner at Mare Liberum. He is a seasoned global finance professional with over two decades of experience in private equity, venture capital, and investment banking at J.P. Morgan, Morgan Stanley, and Franklin Templeton. Most recently, he was a Partner at Americas Frontier Fund, where he specialized in deep tech and strategic investments. His public sector experience includes his tenure as the U.S. Representative to the World Bank, where he was unanimously confirmed by the Senate and oversaw the deployment of over $100 billion in capital. In 2020, he was nominated to serve as the U.S. Ambassador to the Republic of Panama. He is a graduate of the United States Naval Academy and the Wharton School. Erik serves on the board of the U.S. Naval War College Foundation, is on the Board of Directors of Windward, a leading maritime AI company providing predictive intelligence and domain awareness, is a Fellow at the Center for Strategic and International Studies, and an Advisor to Oxford Analytics.
Full Bio: Rear Admiral Lorin Selby, USN (Ret.)
Rear Admiral Lorin Selby, U.S. Navy (Ret.) is a General Partner at Mare Liberum. He is a submarine warfare officer, acquisition professional, nuclear engineer, and technically informed executive and innovator. Admiral Selby served in several high-profile positions throughout his Navy career, notably as the Navy’s 26th Chief of Naval Research until his retirement in the summer of 2023. In that role, he led a distributed team of 3,800 personnel and developed leading-edge technologies for the Navy and Marine Corps, overseeing a $4 billion budget. Prior assignments include his role as the first non-Engineering Duty Officer selected as the Chief Engineer of the Navy and Deputy Commander, Naval Sea Systems Command, and Commander, Naval Surface Warfare Centers. His command at sea was the nuclear fast attack submarine USS GREENEVILLE (SSN 772). He also served ashore as Deputy Director, Navy Office of Legislative Affairs, U.S. House of Representatives. Following his retirement, Lorin has served in a variety of consulting roles advising small and mid-sized technology companies. He holds a B.S. in Nuclear Engineering from the University of Virginia, and an M.S. in Nuclear Engineering and Nuclear Engineer Degree from MIT.
