Getting something square cut like a drag suit. It provides more modesty than jammers without needlessly covering your legs.

If you are doing serious pool competitions, you can get a slicker-than-skin jammer to wear in races.

More explanation.

Generally, most swimmers train in speedo cut suits. They feel more comfortable (this is subjective, of course), and tend to last a bit longer because they're fully lined.

Jammers came about as suit technology improved. As materials had lower drag coefficients than the skin, it made sense to use that material to cover more skin to slide through the water. More recent advances mean compression gear also aids muscle recovery and can improve race efficiency.

More novice swimmers tend to be attracted to jammers for two reasons. They see world class athletes wearing longer suits (these athletes frequently train in briefs, but race in tech suits) and the jammers provide a bit more modesty, which I get -- it's a weird outfit to wear, the speedo.