Acoustical tweezers can manipulate inanimate particles as well as living cells in liquid in 2D using surface acoustic waves and in 3D using bulk acoustic waves. Here, we demonstrate a MHz twin-trap device for underwater manipulation of particles and cell aggregates and show that it operates effectively within a Petri dish and a plastic tube. We also describe a method to visualize in real time the acoustic field using a contained layer of small, high-density particles, which allows the trap to be seen in the same image as the manipulated particle. The device used was made with simple components, integrated onto a printed circuit board, and requires a single electrical channel for excitation. As a result, this device has the potential to be widely implemented in applications such as micro-organism manipulation, in vivo manipulation, and drug delivery.