I'm thinking about going to an over under shotgun for all my waterfowling. Does anyone have any suggestions or advice? I usually only shoot 3 inch, but do they make a 3 1/2 inch in an over under?

Beretta Onyx Pro 3.5
Browning Cynergy
Browning Citori Satin Hunter
Possibly the Remington Priemer as well

just FYI I found this by spending about 10 min looking at manufacturer websites. It's pretty widely available information.

I used to have a Browning Citori that was chambered for 3-1/2" shells. Whenever the shooting position was odd or directly overhead, the recoil from the 3-1/2" shells reminded me to better choose my shots.

Also, be sure to check the conditions you're going to be hunting in. Over-unders don't load and reload very well in tight quarters, like duck blinds and boats. I found it akward, so I went back to a semi-auto.

I think Dan in Alaska makes a good point. Maybe look for shorter barrelled guns. The trick may be to find a heavy short barrelled O/U that isn't SO geared towards competition shooting that its got $1,000 of walnut on it.

Don't know about 3.5" shells. If you've been shooting 3" why do you want to change? Personally can't see the need for 3.5" shells in a 12gauge...any gauge for that matter but that's another topic for another thread. There are alot of "entry" O/U now like the Remington Premier, CZ makes one, Stoeger, Mossberg even makes one. (I handled a Mossberg at the Gander mountain and was amazed. For a $580 double its amazing...time will tell though).