The thick cuticle and waxy layers on the surface of the leaves are seen in plants which grow in low water content areas or xeric areas. They are morphological adaptations of such plants to reduce the rate of water loss.
But for some plants such as hydrophytes, water is available abundantly all around them and they needn't keep the rate of water loss in check. So, in such plants, thick cuticle and waxy layers are absent.
Therefore, a plant without waxy leaves would grow successfully in water rich areas or simply, in aquatic habitat.