There is no prohibition against immersing on the same day you waxed your body. However, sometimes there are remnants of wax left on the body after waxing and those pieces are chatzitzot (barriers). Therefore, we recommend that waxing be done a few days prior to immersion to leave enough time for the wax to come off. If you must have the waxing done the day of immersion, you should wash the waxed area well with soapy water and check carefully for any remnants of wax.
Further, a woman should not wax right after immersion either because, according to some opinions, hairs that are about to be removed are considered a chatzitzah.