Warm water immersion is known to have an effect on human cardiovascular function. This study examines how age (young = 18-30 years and older = 31-65 years) and sex influence changes in blood pressure due to submersion in different water temperatures. Fifty-eight individuals sat immersed to the neck in three different water temperature tanks. Blood pressure measurements (systolic/diastolic blood pressure [SBP/DBP], pulse pressure [PP] and heart rate [HR]) were collected every 6 minutes throughout the duration of the test. We observed significant between-group, within-group, and interaction effects for SBP, DBP, and HR. For PP, significant between-group, within-in group and interaction effects for SBP, DBP, and HR. For PP, significant between-group and within-group effects were found. Additional post hoc analyses found that from baseline to cool immersion, older females (OF) had less change in SBP values compared to younger males (YM) and younger females (YF) and less change in DBP values compared to YM. From warm immersion to recovery, older males (OM) had less change in heart rate compared to YM, and in both the warm and cool immersions, YF lower pulse pressure than YM. Understanding changes to BP during resting water immersion across different ages and both sexes could have clinical applications relevant to both physicians and those responsible for rehabilitation of cardiovascularly-compromised patients.