Based in Silversea's London office, Shanks will lead a team of 71 and report directly to CEO Roberto Martinoli.
He's succeeding Lisa McAuley, who resigned in October and will leave at the end of December.
'We're delighted to welcome Peter back to the cruise sector at a pivotal point in our company's growth and evolution,' Martinoli said. 'His background in cruising and extensive experience in the industry will ensure he is able to effectively lead our team to the next stage.'
For his part, Silversea chairman Manfredi Lefebvre d'Ovidio called Shanks 'the leading expert on the British and Irish markets,' adding: 'I'm thrilled he is joining Silversea and I am sure that thanks to his leadership we will be able to further grow in markets where we are already a renowned and leading luxury brand.'
Shanks has been the development director at Imagine Cruising for the past three years, a time of brisk expansion. The Emirates Group-owned operator of cruise and stay holidays started packaging river cruises, opened its first office in Australia where it's also acquiring Holiday Planet, added two new retail stores in South Africa and began trading in Dubai. Last year overall sales revenue surpassed £100m for the first time with passenger growth in excess of 25%.
Earlier, Shanks spent a dozen years at Carnival Corp. & plc, most recently as president and managing director of Cunard, from July 2009 to October 2013.
Previous roles included chief commercial officer for Carnival UK, managing director of Ocean Village Holidays and SVP Europe for Cunard.