Tweaking your swimming technique can make you a way better swimmer without it even consuming more energy. Which will result in faster times and the exercises being way easier. For beginner swimmer this may will make you feel a lot better, because you will feel that you go forward instead of struggling every time.
Make sure that you reach as far as you can with each stroke. It may seem obvious and easy to do, but in reality it is way harder than you think. Also try to push your shoulder forward with each stroke. This will make your stroke just that bit longer. A good technique exercise for this is to place your hand in front of you two times instead of one. This will help with making your stroke longer, but you have to do it slow and with a lot of attention.
Almost everyone shortens their stroke at the end of each stroke when they get tired or exhausted. This is understandable since it is very heavy and takes lots of efforts, but if you can make it work you will be able to make longer strokes. You can do this by just simply put. Tell yourself that you have to finish every stroke. This will take a lot of willpower, but you got to do it if you want to go faster.
With freestyle kicks make sure you use your hips and relax your knees and point your toes to improve your swimming technique. This also will help with avoiding cramps and will make you faster. Also keep your legs close together, otherwise it will result in drag and that is something you want to avoid. Same counts for keeping your legs high. Your heels should just touch the surface. Keeping them too high will make your upper body sink and keeping them to low will result in drag. So try to find the best of both worlds.
Your head is like the steering wheel for your body. When you are underwater and you tilt your head up you will go up and when you tilt it down you will go deeper. So it is logical that you should think about that within your stroke. Your head should be in line with the rest of the body. This means that the water line must be between your eyebrows and hairline. If you have the equipment or connections, try to let somebody film you when you are swimming. When you see it you can change your mistakes easier and also see where you are not laying straight this will improve your swimming technique by a lot.
Keep calm and do not try to swim like your life depends on it. You should be in control even at higher speeds. Try to swim at a slower pace if necessary. Keep your swimming technique! Also try to keep your breathing in control. Do not breathe too much but also do not hold your breath to long, because that will cause your body to make lactic acid. This will get in your muscles and make your muscles feel a lot heavier. You should always breathe to the side by the way.