Considering it is a tarnished brand, if Merlin did buy Sea World I wonder would they rebrand it with the Sea Life brand.
If Merlin bought Sea World then they would go against everything the Sealife (and therefore Merlin) brand currently stands for. They would inherit Orca, Pilot Whale and Dolphin.
SEA LIFE began as a small seal sanctuary on the beautiful banks of Loch Creran in Oban, Scotland. Almost 40 years, 50 aquariums and nearly 150,000 creatures later we’re now the largest aquarium organisation in the world – but that doesn’t mean we’ve lost our roots. Since we began back in 1979 we’ve held firm to the belief that cetaceans – marine mammals like whales and dolphins – should not be kept in captivity.
But what happened to the Dolphins at Heide Park and Gardaland I hear you ask? Well they got off loaded into other parks while they claimed they were going to create "a marine sanctuary for their retired dolphins". This was in 2012 and has not happened. Also Merlin bought Chang Feng Ocean World in 2012 which have wild caught Beluga whales who were captured in 2009.
So in a roundabout way, if money is involved then I am sure Merlin will not look at its ethical policy and would look instead to the potential profit they could make for themselves and their shareholders.