He started his seagoing career in the late 80s in the offshore industry (North Sea) working mainly on exploration vessels. From here Donnacha spent the early 90s working for general shipping within the merchant navy for a varied number of shipping companies including Dutch shell tankers in Asia and bulk carriers and containers. Prior to joining cruise sector Donnacha spent the last years in the oil fields of Brazil.

He joined cruise sector with Carnival mid 90s and at the end of the decade transferred to shore position within the industry as a chosen career path in various roles in ship management, new builds and human factors.

In 2015 Donnacha was promoted to Senior Vice President Maritime. from there to Executive Vice President for Maritime and Sustainability, making sustainability a key area of focus along with the traditional requirements of ship operational management.