The purpose of this study was to compare energy expenditure (EE), heart rate, and perceived effort during walking in water at several depths versus land in female participants. Eighteen females walked on three separate days on a land treadmill (Land) and in a water treadmill (ATM) at 30° C at 6 speeds. Water depth was at the xiphoid (xip), 10 cm below (-10 cm), and 10 cm above xip (+10 cm). Heart rate (HR), oxygen consumption (VO2) and carbon dioxide production (VCO2) were recorded. RPE overall (RPE-O) and RPE legs (RPE-L) were solicited following each bout. Regardless of walking speed, EE and HR were influenced by water depth, with -10 cm significantly greater than xip, +10 cm and Land, and xip significantly greater than +10 cm and Land (all p < 0.001). Land EE and HR were similar to +10 cm. RPE-O was significantly higher for -10 cm vs. xip, +10 cm, and Land, while xip was greater than Land. RPE-L was greater for -10 cm vs. xip, +10 cm and Land, while xip was greater than +10 cm & Land. Our results showed that small changes in water depth influences exercise EE, HR and RPE. These differences are attributed to a changing relationship between drag resistances and buoyancy in water.