Soak dried wakame in a generous amount of water in a medium sized bowl and let them hydrate. Or if it's salted fresh wakame, drain water twice and soak it in water for five minutes. Don’t soak them for more than five minutes. (note 1)
Rub cucumber with a pinch of sea salt until moisture appears on the surface. Remove the moisture with running water, and dry the cucumber with a kitchen towel. (note 2)
Cut off the head and the end of the cucumber. Slice cucumbers with a slicer or a knife.
Cut tomato into cubes.