When induced by bottom heating in a horizontal fluid layer which is characterized by forced motion or solute stratification, buoyancy driven flows may assume a variety of forms. The flows, which are examples of mixed or double-diffusive convection, can strongly influence heat transfer or the entrainment of stratified fluid. After reviewing general aspects of each form of convection, emphasis is placed on mixed convection in a horizontal, rectangular channel and on double-diffusive convection due to thermally driven mixed layer development in a solutally stratified fluid. Flow conditions are described, and experimental and theoretical results are presented for related heat transfer and entrainment parameters.