Assuming $\mathsf{AC}$, it is easy to show that every infinite set can be ordered in a dense order: for a set of cardinality $\aleph_0$ we can take a bijection into $\Bbb{Q}$; and for a general infinite cardinal $\kappa$ we can take $\kappa$ copies of $\Bbb{Q}$ (with an infinite lexicographic order).
What is the strength of the statement "every infinite set can be ordered in a dense order"? Is it equivalent to $\mathsf{AC}$?
It is so weak that it won't even prove the Boolean Prime Ideal theorem. Indeed, even assuming $\sf ZF+BPI$, the principle "Every infinite set can be densely ordered" is not even enough to prove the Kinna–Wagner Principle.