Bathmate's original model, the Hydro7, is their entry-level pump, offering a moderate level of pressure for a more gentle introduction to penis pumping. The Hydro7 is currently the only model in the Hydro series, and is best-suited for users whose penises are between 5 and 7 inches long when erect.

Bathmate's unique penis pumps employ hydro-vacuum technology, meaning that they use water rather than air to create a vacuum. The Hydro7 is designed to be filled with water before the penis is inserted. Pressing the pump against the body creates a seal, and pumping is done by pushing the device against the body, compressing the base. The displaced water is forced out the one-way valve at the top of the cylinder, which creates the vaccuum, drawing blood into the penis and quickly causing it to become erect. The Hydro7 can also be used without water.

According to Bathmate, there are several benefits to hydropumps when compared to conventional penis pumps. With water, the force of the vacuum is more uniform than with air, ensuring that the all the veins in the penis are equally stimulated. Warm water also opens the pores and softens the skin, allowing for greater elasticity and less chance of injury.

The Bathmate Hydro7 is manufactured in the UK from high-quality, body safe materials, including durable polycarbonate, silicone, and stainless steel. It is currently available in Crystal Clear colour. This model is best-suited for penises that are between 5 inches and 7 inches in length and less than 6.5 inches in girth when erect.