For shape/design:
* Hydrodynamic: This emphasizes the efficient movement of water around an object.
* Fusiform: Describes a spindle-shaped body, which is common in aquatic animals and is inherently streamlined.
* Sleek: This is a more general term for a smooth and elegant shape.
* Contoured: This emphasizes the specific shaping of the object to reduce water resistance.
For movement:
* Fluid: This refers to smooth and effortless motion through water.
* Graceful: This suggests an aesthetically pleasing way of moving through water.
* Effortless: This highlights the ease with which something moves through water.
Other options:
* Efficient: This emphasizes the low energy expenditure required for movement.
* Low-drag: This focuses on the reduction of resistance from water.
The best word to use will depend on the specific situation and the desired emphasis.