One way to increase power is actually to purposely increase drag. Now, if you increase drag you're going to swim slower, and it's going to be harder, so obviously this is not a technique we want to use when racing! BUT for training it can be super valuable. I remember back in high school we would wear 3 baggy swim suits to train in, and sometimes throw on panty hose as well! Train like that all the time and then in the race wear one super tight (no drag!) paper suit and it was like magic how fast we could go.
These days a lot of us (me included!) use tools like buoys and paddles and sim shorts to make us swim faster. I definitely believe there is a place for this... #1 for athletes who are discouraged by swimming, using tools to see faster paces is motivating. If that athlete ends up liking swimming more (or even just hating swimming less!) and therefore ends up actually swimming more, well, that's going to benefit them. #2 for athletes who have training partners slightly faster than them, using tools to help you keep up and complete a whole long main set of 2-3k I think can be a good call. Feeling like you're 'in it' while working with others is motivating and everyone works harder in this scenario. So in my mind, if a pair of sim shorts is just enough boost to keep you engaged in the workout with your training partners, then by all means, use the tool!
But let's go back to purposely creating drag. How and why would you do this? Well, when drag is high, a swimmer has to create more power to move forward through the water. If you purposely create drag so you're forced to create more power, and you get used to creating more power because you swim with drag a lot, you're going to get stronger while creating a habit of pulling really effectively! You can create excess drag by tying your feet together with bands, by wearing a specifically designed drag suit, or by pulling a parachute while you swim.
Bands are an easy tool to make and use- just cut and tie an old bike tube tight around your ankles and you've got your drag. I used to swim a ton with bands but have gotten away from it recently, maybe because my training partner Mark is so freaking FAST with his bands on that we can't really swim together when we both use bands. Seriously- bands don't slow that guy down at all. You know why? Because his turnover is insanely fast. I'll have to count his cadence sometime but I'd guess that it's up around 90 strokes/min. Maybe higher? If you combine an effective underwater pull with cadence like that, drag isn't really going to be able to slow you down. It takes a hell of a lot of specific fitness to sustain a cadence that high through a whole workout. Mark has that fitness so it works for him.
Another way to create drag is to wear a drag suit. So like I said in high school we would wear 3 suits- the bottom one was tight but then we'd wear 2 that were super loose and ripped up on top of that and it would slow us down enough that we had to work harder to hold pace through a workout. Finis makes a drag suit that looks like a mesh (male) speedo and it has giant cups/holes that really create a ton of drag. It's been a long time since I used my drag suit but since I was swimming alone I got it out today. Swam 5x100's with it and it slowed me down by 20-25"/100, and swimming with it was HARD work! I find the drag suit way harder to swim with than bands, but this isn't the case for everyone. Even though it's harder, I like it better for forcing power because it still allows me to use the mechanics of a kick. That said, I'm not strong enough at the moment to do much volume using this suit. I can do more volume with bands through a workout before feeling like I'm really losing it. When I'm strong I can do whole (long) main sets using bands, and we've taken them for use in the ocean as well to slow us down for open water swims. No way I'd even consider wearing this drag suit for a long ocean swim. #NoDrowning
Another way to create excess drag is to swim with a parachute. I've actually never done this, partly b/c I don't have a parachute and partly b/c I can't really imagine that I could use one in the pool I swim in without it getting in the way of other swimmers? It's a long course pool with no lane lines so I can see someone getting caught up in it or something... Maybe it's more user friendly than I'm imagining, but the concept is the same as drag suit so when I want drag I'll just go with the suit. You could probably make one of these though with a race belt, a dog leash, and a plastic bag.
Anyway, there you go. If you feel like you're not creating much power when you swim, try swimming with bands. If you can't get across the pool with your feet tied together, then you've confirmed that indeed you're not creating much power. Get (or make) a drag suit and swim short repeats 25's and 50's and then go back to regular swimming without the drag and see if it feels more powerful and efficient? I did a set of 50's today where I alternated 2 with drag, 2 without drag... repeat repeat... Fun to take the drag off and feel slippery like you're moving through the water so much better! My goal is to bring my drag toys out more often and get good with them again. I think this is a game changer when it comes to swimming faster. It's probably best done when swimming alone but you could also use drag to equalize things if you're swimming with someone who is a bit slower than you.