Calcium channel blockers don’t typically pose problems for divers: they relax the walls of blood vessels, reducing blood flow resistance and thus lowering blood pressure. In some cases, especially in moderate doses, a change in position from sitting or lying down to standing may cause excessively low blood pressure and a subsequent momentary dizziness. This postural blood pressure change may be a cause for concern with divers, but calcium blockers appear to have no other adverse reaction for diving.