Waters was most recently the executive chairman, UK and Ireland at Dentsu Aegis Network, having previously been CEO of Asia Pacific for nine years.
Before the signing, DAN owned 66% of Merkle shares with an option to buy the remaining 34% in Q3 2021.
Chairman and CEO of Publicis Groupe Arthur Sadoun said it is, however, still too early to predict the full impact it will have on its clients and its business.
Among the list of measures include temporary salary reductions, with the top management team taking the highest percentage cut.
The Groupe also appointed CEO of Publicis Media Exchange APAC, and a chief product and solution officer, Publicis Groupe APAC.
Clark is recognised for her modern leadership approach that includes her philosophy "Lift as you climb", translating to taking talent with you as you grow.
Seow's appointment comes shortly after APAC MD Paul Mottram left to join Zeno Group.
The review comes shortly after CEO Miguel Patricio said in February that Kraft Heinz plans to increase media spend by 30%.