Some trans* guys avoid swimming altogether. It is too difficult, too triggering, but there are ways to swim and still be read as male. It depends on your build, your comfort zone, and how much money you may have available as to what approach would be best for you. If you notice when you are on the beach, not all men swim with their shirts off, so we do have the opportunity just to be another one of the guys. Perhaps not in the way we may want, but there are ways to have fun and to be able to swim.
The first option would be your basic t-shirt with a sports bra and/or a compression shirt to bind. Out of the three possibilities, this is the cheapest. It depends upon your build as to how effective the binding will be. The second option would be to use some sort of rash guard or a wetsuit. Rash guards, wetsuits, and other typical swim tops tend to have at least some binding qualities, and with the right one, your chest can appear the same as it would in a binder. The last option would be to buy binding swimwear, such as the shirt you can buy on Underworks, which can even come with matching trunks. I bought mine last summer and have loved the freedom it gives me to feel like myself. It can be a bit of a trial to get into, but it binds well and is comfortable. The only thing I dislike about it is the binding material stops at about two-thirds length, making it feel a little off-kilter because it can ride up if your swim trunks are loose.
Some guys get uncomfortable while wearing any type of swim top because between binding and then layering with larger shirts to give a more effective appearance of a male chest, wearing something tighter and more revealing can feel very strange. You can swim in binders, though generally it isn’t recommended. It can be very uncomfortable and bad for the binder itself. It also depends on how tightly you bind. If your binder in any way constricts your breathing, you should not wear it to swim because it can be dangerous.
The other problem with swimming is it can be triggering. Many of us deal with dysphoria every day. There are the constant reminders. Swimming for me it is one of the things I love most, but it can be triggering. But there’s nothing like diving under a wave. It is hard, but I hope this post gives you some options so you can swim. Hudson’s FTM Resource Guide is another great resource to find more information.