Which type of water you’ll most often paddle can also help you decide between a sit-on and sit-in kayak. There are advantages to both.
Seat height impacts stability. Seats mounted higher above the water or the kayak floor are common with fishing kayaks. You get increased range of motion for casting, and you can see greater distances in clearer water to spot fish. Higher mounted seats also decrease stability, while it increases with lower seats.
Sit-ons offer easy entry into or out of the boat. If you plan to go swimming, this could be your boat. Sit-on kayaks have drain holes or scuppers that make them self-draining. The combination of self-rescue and self-draining features make them ideal for paddling solo. The open design also exposes the paddler to the elements, such as waves washing over the deck, wind, or cold temperatures. Sit-on kayaks are generally wider, have a higher initial center of gravity, and are more stable. Sit-ons are also virtually unsinkable because of the closed design of the hulls.
Sit-ins are the most popular kayaks for their enclosed cockpits and higher degree of secondary stability. What that means is the kayak tends to stay upright when leaned on its edge for turning and paddling in waves. The narrower hull of a sit-in makes it faster. Less paddling effort makes them ideal for long-range paddling. Sit-in kayaks offer protection from the elements. Water stays out of the hull—or the interior cockpit space—unless you capsize or get caught in a downpour. You get comfort in cold weather, and there’s room for bulkier items like storage bags.