When an object is placed in a fluid, it experiences a buoyant force that opposes its weight. This buoyant force is equal to the weight of the fluid displaced by the object. If the object's density is less than that of the fluid, it will float. However, the object will not necessarily leap out of the water.

Here are some factors that can affect whether a buoyant sphere will leap out of the water:

* Density: The denser the sphere, the less likely it is to leap out of the water. This is because a denser sphere displaces less water, resulting in a smaller buoyant force.

* Size: The larger the sphere, the more likely it is to leap out of the water. This is because a larger sphere displaces more water, resulting in a larger buoyant force.

* Viscosity: The more viscous the fluid, the less likely it is for the sphere to leap out of the water. This is because the viscosity of the fluid resists the movement of the sphere.

In addition to these factors, the shape of the object can also affect whether it will leap out of the water. A sphere is the most buoyant shape, but other shapes, such as cylinders and cubes, can also float. However, they are less likely to leap out of the water than a sphere.

In summary, buoyant spheres don't always leap out of the water because of the interplay between various factors, including the sphere's density, size, the viscosity of the surrounding fluid, and its shape.