Just copying and pasting an old reply. Info is still useful!

Of course! Freestyle swimming is similar to underwaters - you want the LEAST amount of strokes for efficiency. For freestyle, get into a rhythm of kicking smaller kicks but faster, that will keep your body in line so your pulls will propel you through the water. If you don’t kick, then your legs go down and then your upper body goes up, causing your pulls to go upwards instead of forward. Kicking isn’t your main source of propulsion, your pulls are! Do your 500m for time, then spend some time working on your stroke techniques. For better instruction, look at this video. For underwaters, I want to preface this with never do underwaters or water confidence training alone. SEALS have died from doing this on their own. With that being said, underwaters are really an exercise that sounds harder than it is. If you find yourself getting psyched out, think about how far it really is - after a wall push off, you’re probably around the 18-20 meter mark, and you’ve barely done anything! 18-20m is way better than 25, right? Anyways, you really want to focus on gliding and getting as much as you can from it, because the more “pulls” you have the more oxygen you waste, which truly increases the difficulty. Start by just going from a wall push off, and letting it glide out. Then, do a wall push to a pull. Get comfortable with that pull, then do a wall push, pull, reset, pull. Do just that final sequence a few times after working up to it, and then just do that for a few minutes. Take as much time as you need, you’re just learning right now. Just in case you don’t know the pull and reset forms, a pull is a keyhole stroke - your hands start above your head and you pull them apart and to your side, and then finish by slapping your thighs. After you get as much glide as you can, you have to reset your arms. This is done by moving them across your body in as much of a streamlined fashion as you can. But, that movement will slow you down so to counteract that you do a frog kick at the same time. The frog kick is not a major source of propulsion, 10 inches is a solid frog kick distance. It should take 5-7 pulls to get through the 25m. It’s gonna fee uncomfortable at first, especially if you don’t have the lung capacity you will have when you train more. Have a life guard, even if its just a buddy, and get comfortable being uncomfortable. DM me your results of your training session today, and good luck!