You wont get lost going to atlantis. just walk along the beach in the direction of
Icmeler (opposite end of
marmaris from ataturk statue and marina) Basic Directions...... Gima on main road to Icmeler, walk towards beach, turn right when you meet the beach and walk along a good few hundered metres, and you will see it no problem.
You wont be able to miss it.
As for the aquadream, I believe it is up a steep hill behind the Migros that is by the Blue Bays roundabout, again in the direction of Icmeler, but someone here should be able to confirm this for you