Arqualeus' Bouyant Architecture

Arqualeus was a great architect along with a wizard, inventing this spell to make his spire float. Much later, sailors discovered the spire and a city that was adrift on the ocean was born, with much more infrastructure than you would think due to the still-lingering enchantment. The target (inanimate only, sorry murderhobos) Will become buoyant and never sink, no matter it's weight. Any item underwater which gains this enchantment will fall upwards, but at half speed and half terminal velocity.