If you ask most reenactors what men wore to swim in during the mid-19th century, you would probably be told "nothing - men always swam in the nude."
Well, I'm sure there certainly were times when men swam in their skin, but a bit of research tells us that it was definitely not a case of "always".
This scene, "The Bathe at Newport", by Winslow Homer circa 1858, shows a good reason why - in America, bathing was not gender segregated, as on the continent - and while the Victorians were not the prudes they are ever so frequently portrayed as, group nude bathing was definitely not a socially acceptable activity!
Clues to what men actually did wear, are tantalizingly few. I choose to use this example in the collection of the McCord Museum as my inspiration. The original is wool, trimmed with braid.
The museum's description notes that men's swimming suits of the period were closely styled on underwear - and that's exactly what I used for the basic shapes when creating my custom pattern.
I took the pattern pieces for men's drawers and a square shirt and combined them into one piece.
My initial "muslin" (actually an old flannel sheet) was a bit short in the torso, so I added an additional 3" - thus, the piecing you can see on the muslin.
When I first asked Robin if he would be willing to wear a period bathing costume, he readily agreed: if it was ORANGE, so if he ended up floundering in the waves, we could find him. As fate would have it, on our first attempt to find appropriate fabric, what did we find but bright orange wool! However, it was blanket weight and would have had him floundering in the waves for sure, so we settled on this color scheme instead
And behold, my version of an 1860's male bathing costume, which has come to be nicknamed the "Civil War Onsie"! It was never my intention to 100% replicate the McCord Museum piece, but to use it as reference. The basic shape is very close, but I used bands of red wool as my trimming and the mother of pearl buttons were great accents.
As the "test driver" so to speak, Robin reports that it is both functional and comfortable.