Entry level DSLR bodies were never popular for underwater photography, primarily because the cost of the camera body comes to a fairly small portion of the total rig cost (lenses, housing, ports, strobes, viewfinders, etc). The total cost of such a rig can easily exceed $10,000, which makes dwarfs the difference between, say, a $700 D3200 and a $2000 D500, yet a rig built around a D500 is massively more capable.
Technically, you can get an Easydive Leo3, which will support your D3200 as well as a host of other cameras, but the cost of a complete rig (housing, ports for fisheye and macro lenses, a pair of strobes with necessary hardware and some accessories) comes out to about $7500 not including shipping and taxes. You can get a second-hand ready-to-dive D500 rig for less than half that.
Edit: Actually, scratch that - I forgot that D3200 doesn't have a focus motor. Pretty much everyone who shoots underwater with an APS-C camera uses the Tokina 10-17mm fisheye lens, but its Nikon F-mount version uses screwdriver autofocus (the focus motor is located in the camera body rather than the lens, and drives lens focus via screwdriver-like coupling), which means it won't autofocus on your camera. This makes it largely useless as an underwater body, hence no manufacturer making a housing for it.
