The range of options here includes everything from going “commando” (i.e. nude/wear nothing, au natural) to wearing a garment specifically designed to be worn under them, and everything in between- including everyday underwear . Ultimately, it depends on one’s preference. However, the type/style of swim shorts will certainly persuade and/or dictate what one wears (or doesn’t wear) underneath them as well.
The sport/activity requires one to use, predominantly, their chest and arm muscles. This results in the upper torso becoming rather muscular. And, this, in turn, causes a natural reduction of breast tissue and fat, and, ultimately, smaller breasts.
A “heat” is considered a round/”wave” for each event during preliminaries (and sometimes semifinals) of a swimming event. How many heats there are in an event will depend on the number of lanes available and how many swimmers are competing in the event.
The point of compression shorts is in the name- it is compression. However compression shorts should not be constrictive. The compression shorts should be tight enough to feel the compression, but not tight enough to feel uncomfortable.
Some practices one can take/put into place to prevent tanning while swimming as well as to protect one’s skin/hair from the water/any chemicals in the water include,
The only two branches that require swimming (not just water safety/survival) as a mandatory skill prior to enlistment, during basic training, and throughout one’s military career are the U.S. Navy and U.S. Coast Guard. All other branches of the U.S. military, at a minimum, may include water safety/survival skills during their basic training, as part of training for other specialized jobs within their branch, and/or throughout one’s military career (depending on their specific job), but it is not mandatory for enlistment unless you are enlisting into a specialty job and/or at a higher rank within that particular branch which requires such skills.