Other boys at annual summer camp, when I was age 8 through 10 beginning in 1957. There were 16 campers to each small 1-room cabin, 15 boys and 1 college-age camp counselor. We saw each other in tighty whities every day while dressing, because that was the most common underwear for boys & young men back then. You only had 2 main choices in the US: boxers that were popular with older men, and white cotton knit briefs. Other kinds of undershorts available today didn't yet exist, nor did colors except for boxers.
During our overnight hikes we'd go skinny dipping in a creek, having brought no swimsuits with us, 2 cabins going out together making 30 of us total. And after swimming, since we brought no towels along, either, we'd put just our Jockeys back on while air-drying on the flat rocky shelf alongside the swimming hole.
All these boys and a couple of adults wearing nothing but identical white briefs, very 1950s conformity, lounging and milling about in the sunlight, some naked swimmers still in the water or standing at the edge, very homoerotic, very Thomas Eakins. And I think I remember it so very clearly because I was just beginning to feel an attraction for other boys, and an interest in their bodies.
It was also the first time I saw totally naked adult men, right out in the open in broad daylight for long periods. Not a momentary glance while dressing, that left more questions than answers, but a chance to actually study the nude adult male anatomy in many different casual postures, and it gave me a strange thrill. Pleasant memories.