T.T.
Camp America in Chalfont and Elbow Lane Day Camp, close by, both in Bucks County, have (or at least had, when my kids were younger) special, half day programs for 3 year olds, with special, low fees. It cost less to send kids that age to Camp America than it did to our preschool camp...and with all the many things that a true, all around camp offers! Smart marketing by the camps! (Both camps have websites, of course, so you can see what current fees and programs are.) We know kids who go to both.
We debated between America and Elbow Lane but ultimately chose Camp America because it is ACA (American Camping Association) accredited, and that was and is important to us. Camps have to do so much to maintain their accreditation, and we wanted a camp that would meet those requirements. (You can go to the ACA website to look into this.)
Our preschool camp was wonderful, too, and certainly offered enough for a 3 year old.
Personally, I would look at preschool camps and not daycare camps, unless you truly need daycare services.....
As for swimming, I don't remember what Elbow Lane has, but Camp America has 4 pools, and my kids really learned to swim there. One pool is a wading pool, for the real little kids. My experience is that kids at camps don't wear vests because they learn to swim!
Our preschool camp had a wading pool and a small, above ground pool, without the water too high. The kids have a great time there, too, and also learn how to swim...or at least start learning how to swim!
Good luck, and have a great summer!