Aquatic animals have evolved complex mechanisms and body motions to achieve underwater propulsion efficiently. One component of their motion is their ability to actively bend their bodies, a form of active flexibility termed as morphing. The propulsive device considered in the present study is a foil undergoing combined heaving and trailing-edge morphing motions. A simple form of morphing described in literature is realized to investigate the effect of phase difference between heaving and morphing motions. Two scenarios of morphed foils representing high and low morphing are chosen for the study. The cases are further analysed using vorticity and foil surface pressure plots to identify the causes for thrust variations across phase angles. The timing and positioning of the leading-edge vortex (LEV) and the trailing-edge vortex (TEV) are scrutinized with relation to the position of the morphed foil to understand the forces on the foil.