Force in Diving:
There is a lot of force used when swimming, especially when trying to overcome the drag and friction brought on by the water. To begin, when you are swimming you have to overcome the drag from the water. The drag of the water is the thing that grabs onto anything loose on you-whether it be hair, clothing, or anything else- and it uses it like an "in-water parachute" to slow you down. In order to overcome the drag, you have to be as swift with your movements as possible, and wear clothing that the water resistance will slide right over. This is why swimmers tend to wear as little clothing as possible, shave any visible hair, and wear swim caps.
When you are diving off of the platform at the beginning of a race, you use force against the gravitational pull of your body to the platform. Your legs are bent, and act like springs, so as soon as you push up, your body forces yourself off of the platform and into the air, where you will soon glide into the water. You start off with a balanced force, of gravity pulling you down, but the platform pushing you up to keep you steady. Then, when you jump off of the platform and get into the water, the buoyancy of the water overcomes the gravitational pull, and creates an unbalanced force, so you don't fall to the bottom of the pool.
Friction in Swimming:
When you are swimming you are almost always at battle with friction. Friction is part of the drag that catches on to you when you are swimming. As well as friction is the water resistance that is trying to slow you down when you are swimming. Water resistance is like air resistance, both coming from fluid friction, except they have their differences. Air resistance is when an object is falling or flying through the air, but the air slows it down to a point of stopping based on its surface area. While water resistance, or fluid friction, is when an object is going through water and the water pulls on it to slow it down, or grabs onto it to try and have a bigger force.
Gravity in Swimming:
When you are swimming, you face a lot of gravity, that happens throughout the entire time that you swim, from start to finish. First, when you are on the platform, the gravity and static friction are what's pulling you down, they keep you on the platform, and help you not to fall off. At that point gravity is up against the force applied by the platform to keep you centered and balanced.
Then when you dive off of the platform, gravity is the force that pulls you back down to the ground and allows you to slip into the water to start swimming.
(Weight is the same thing as Gravity in this diagram.)
Lastly, the entire time that you are in the water, gravity is trying to pull you down. While the buoyancy is managing to keep you up on the top of the water, and going forward. Although, if the buoyancy wasn't there, you wouldn't be able to stay at the top, you would just keep sinking to the bottom because the gravitational pull would bring you down.
Inertia in Turning:
When you are swimming and you get to the wall and have to turn, you flip yourself, and somewhat stop your motion in one direction and change it to the other. This is represents Newton's laws of inertia, because "An object in motion tends to stay in motion unless acted upon by an unbalanced force." You, the swimmer, are staying at a constant speed of motion until you get to the unbalanced force, the wall, where you slow down and have to turn, like what it shows in the diagram.
Momentum in Swimming:
When you are swimming and you kick your legs to pump water, each pump creates an action force. Which allows the water to create a reaction force that pushes you forward in motion, and allows you to keep your momentum.
Another thing that allows you to keep your momentum is your hand and arm cycle when swimming. When your hand and arm pushes down on the water, it creates a force that the water duplicates and sends back to your hand and arm, allowing you to move forward with every push.