You can use a whitewater kayak on a lake, but it will be less than optimal. It will be hard to control, slow, tend to tip, and less efficient.
Ideal for whitewater
As the name suggests, whitewater kayaks are specifically designed to meet the requirements of kayaking on whitewater. They are generally used on rivers with fast stretches of water or along very rough and rocky waters
They are usually 4 to 10 feet in length and are designed for moving down fast flowing courses and rough waters. Made from Hard wearing rotomolded plastics they are usually sit-in-only.
Playboat Whitewater Kayaks on lakes
These are the shortest whitewater kayaks they have a scooped bow and blunt stern providing good maneuverability. They gain speed by traveling through rapids. They are highly agile and excel at navigating rocky waters. They are unstable because of their design and this can prove to be a disadvantage if they are used on a lake. Moreover, the scooped bow of playboats makes them very slow in open waters. Because they gain speed from fast-moving rough water and the water in the lakes is very calm.
Whitewater Creekboats on Lakes
Longer than playboats, creek boats have more volume and can run low volume waterways. Due to their stability, they can be used on flat stretches of water. But they are not built for comfort or long journeys and kayaking on the calm waters of lakes usually leads to long journeys that call for comfort and creek boats can prove to be rather uncomfortable after a while because they are designed to negotiate rapids and whitewater kayaking is usually for na shorter time.
Slalom Whitewater Kayak on Lakes
A professional may have a better chance at kayaking on a lake in this whitewater craft. However, for a beginner, it is a very bad idea. Slalom kayaks are designed specifically for racing downstream or upstream. They are very fast on moving water and it is quite hard to control these crafts. In fast-moving waters, they gain acceleration and speed by the rapids themselves.
The water carries them forward. But if used on lakes, beginners will not be able to control them and paddle in a straight line. On lakes, it is far less unstable and can tip over. If you have to use it on a lake it is better to add a skeg that can slide over the rear because that makes it easier for the kayak to move in a straight line. On calm lake waters, it is hard for this craft to stay upright as it has a steeper learning curve. It is not designed for comfort as the sport it is used in is for a shorter period of time than kayaking on lakes.
Lake kayaking is usually for long stretches of time and requires a craft with comfortable, adjustable seating. Therefore, slalom kayaks are not suitable for use on lake waters. Slalom boats usually accommodate one person so if you want to enjoy a kayaking trip with family and friends this kayak is not ideal as it will not be able to accommodate more people. It also lacks room for storage as it is generally used in short races where a lot of storage space is not needed.
Some whitewater kayaks might be able to adjust to lake waters if they are controlled by experienced professional kayakers. This can also help them develop their skills further. But it is advised to not use them on calm waters as whitewater kayaks are specifically designed for fast-moving water.
Calm water can limit their mobility and make them harder to control and less efficient as well. Moreover, they are high-performance crafts with specific weight-range and are usually very light. Their ease of use will suffer greatly if they have more weight to carry than they are designed to.