Countercurrent swimming machines made their appearance in the 1970s, initially in the form of pump-driven jetted streams, which caused a certain amount of turbulence and an un-natural swimming environment. They were followed up in the 1980s by propeller- and paddle-wheel driven machines. These provided a smoother stream of water. Many users find them relatively easy to swim in, though some are bothered by the considerable chop – inherent to these small pools, especially when performing symmetrical strokes such as the breaststroke or the butterfly. These machines are also criticized for being expensive, noisy, and wasteful of energy. (A typical machine requires special power connections delivering 3 to 4 kW for the pressure-driven machines, and 6.5 to 11 kW for the volume-driven machines, aside from any power needed to heat and filter the water—usually an additional 5 kW for an electric heater and around 1.5 kW for a pool pump and filter.)

Two types of exercise machines make up the second group. Hybrid systems - self-contained micropools similar to the counter-current type but using a flexible tether to keep the swimmer in place are one type. These systems, being human powered, need neither machinery or electricity but have to be carefully designed to suppress wave formation. The second type allows a person to remain on dry land while simulating certain swimming strokes. Machines of the latter type however can not compensate for the weight of the body and the limbs and thus deprive the user of the benefits of exercise in an aquatic environment. However, the higher effort required by such machines, in the absence of the metabolic effects of immersing the body in water, makes these devices more effective than true swimming if one's purpose is to achieve weight reduction. Similar in purpose, but not qualifying as swimming machines since they require access to a swimming pool, are various tether systems.

These systems depend on one or more pumps. The best ones are engineered to maximize the volume of water delivered, at the expense of high head which here is not needed as the water need not be lifted, only set in motion. Discharge rates of 13 L/s (200 US gal/min) and more are possible, from motors of three or four horsepower (2 or 3 kW). One of the earliest models on the market - introduced in 1973 - was the Badujet which is available only in the form of a bare propulsion system, to be installed into either an existing or newly-built pool. Of the models known about and tested the absolute worst machine developed has been the Endless Pool. The swim can be smooth once the owner has spent considerable time "tuning" it, and the power consumption is outrageous. This product is equivalent to the dreaded "SUV" we're not supposed to drive any longer.

Also in this category are a number of swim spas, usually fiberglass shells equipped with several pool pumps to set the water in motion. Seen as more convenient since they come pre-assembled, the quality of the swim has been criticized by indoor swimmers as being somewhat turbulent, as the strength of the current comes from the speed and pressure of the discharged water, rather than its volume. Contrary to this, triathletes and other sea swimmers have praised the system due to the turbulence created by the jets mimicking the behavior of the sea, improving stamina and general fitness.

Swim Spas, as the name suggests, are a combination of a spa (or hot tub) and an exercise pool. Single-zone models are typically a fibreglass pressure-driven exercise pool which has swim jets at one end, and one or more spa seats fitted with massage jets at the other.

In the 1980s Monarch Spas developed the dual-zone swim spa so that pumps and other equipment needed for the pool, could also be used to power a separate spa. Today, the advantage of the modern dual-zone system is that the two pools can be at different temperatures using different chemicals - the Hot Tub (using bromine), is hot enough for relaxation and massage, while the swim zone is cool enough for strenuous exercise (using chlorine).

In 1994 HydroWorx patented its first therapeutic pressure-driven pool, the HydroWorx 2000. The new design utilized an underwater treadmill along with pressure-driven jets for rehabilitation. Dr. Paul Hetrick, founder of HydroWorx, got the idea after witnessing a horse trainer at Penn National Race Course using an underwater industrial-strength treadmill to rehabilitate injured horses. Later versions incorporate an underwater monitoring system that projects an image of the patient onto a monitor so therapists can adjust treatments in real-time .

In the 1980s a new type of machine made its appearance. In an attempt to correct problems of turbulence and resulting discomfort from swimming against a jet of water, systems were devised to set the water in motion in a smoother fashion. The first, in 1984, was the SwimEx, developed by Stan Charren together with two MIT-trained engineers. This machine, consisting of a fiberglass pool with the machinery housed in an adjacent compartment, sets the water in motion by means of a paddle-wheel, thus generating a steady stream of water as wide as the swimming pool itself.

In the late 1980s the Endless Pool was developed by James Murdock, in an attempt to build a less-expensive alternative to the SwimEx. This machine places the water-moving equipment - a large propeller encased in a stainless steel box and powered by a remote hydraulic pump, and its stainless steel water circulation tunnels - inside the body of a vinyl-lined metal pool. Its stream of water is narrower than that of the SwimEx, though the swimming experience is comparable. A couple of copy-cat systems have sprung up since its introduction.

Around the same time, the Swim Gym, a propeller-driven propulsion system developed by engineer Peter Davidson became available commercially. This machine is encased within a large (10" diameter) PVC tee which is then incorporated into the concrete wall of a swimming pool. It delivers a current equivalent to that produced by Endless Pools.