The boat conformations have higher energy than the chair conformations. The interaction between the two flagpole hydrogens, in particular, generates steric strain. Torsional strain also exists between the C2–C3 and C5–C6 bonds (carbon number 1 is one of the two on a mirror plane), which are eclipsed — that is, these two bonds are parallel one to the other across a mirror plane. Because of this strain, the boat configuration is unstable (i.e. is not a local energy minimum).
The molecular symmetry is C.
The boat conformations spontaneously distorts to twist-boat conformations.  Here the symmetry is D, a purely rotational point group with three twofold axes. This conformation can be derived from the boat conformation by applying a slight twist to the molecule so as to remove eclipsing of two pairs of methylene groups. The twist-boat conformation is chiral, existing in right-handed and left-handed versions.
The concentration of the twist-boat conformation at room temperature is less than 0.1%, but at  it can reach 30%. Rapid cooling of a sample of cyclohexane from  to  will freeze in a large concentration of twist-boat conformation, which will then slowly convert to the chair conformation upon heating.