Question

Why do objects float in liquids denser than themselves?

Answer 1

..so when something will be denser than water it means it has a greater surface tension which helps it in floating on water surface

Answer 2

The bouyant force is the one causing the object to float, it acts upward and balances de weight of the object.

this force depends on the density of the fluid, look for "archimedes principle" or "bouyant force" in your book/notes/internet !