Cutting main drain line to relocate equipment

[sevver]

I'm concerned about the amount of water coming in when I cut it. Can I put one on blind under a couple of feet of water?

I have put them on blind under water many times. It is a simple matter of tightening a band with a nutdriver. I have repaired live watermains under several feet of water several feet deep underwater with the walls coming down around me, trust me it won't be too hard. But you should have everything ready in advance so it will be a quick swap.