What took them so long to find Atlanna?

Maybe their tech/tracking stuff is useless outside of water. What would make sense was to work out the probability of different locations along the coast she would have likely washed up on. Then sent out scouts which would have had to be high-borns or whatever they called them as they are the only ones that can breathe air. Whether that was too much of a risk I don't know. They can't exactly send their stormtroopers door to door to places on the coast with a photo (do they even have photos?) of Atlanna without broadcasting their existence to the world.