Jarhead: You the Fish Boy from the TV?
Arthur Curry: It's Fish Man.
Queen Atlanna: I am Atlanna, Queen of Atlantis.
Thomas Curry: I am Thomas, Keeper of Lighthouse.
Queen Atlanna: A king fights only for his own nation. A hero fights for everyone. You fight for everyone.
Mera: You think you're unworthy to lead because you're of two different worlds? But that is exactly why you ARE worthy!
Orm: My brother has come from the surface... to challenge me for the throne!
Arthur Curry: I call it an ass-whooping.
Arthur Curry: My father was a lighthouse keeper. My mother was a queen. But life has a way of bringing people together. They made me what I am.
Answer: Because what they're looking for is in the ocean. The maps, the ancient texts and markers leading to the trident. It would seem odd to search for Arthur on land then return to the ocean.