Definitely aquatic. The H. corymbosa sold at Petco is in the emersed form. It should convert to submergent growth after a few weeks.
Someone on another website warned that this plant after several weeks will start to die underwater. And then when I saw it at petco (knowing how petco always sells non-aquatic plants) then I really became curious whether this plant would survive in water. BTW, the one at petco has much darker and smaller leaves....looking nothing like these pics.