Bubbles in polyurethane now what?

I’m redoing the floors in my house. I left my roommate to put a coat of polyurethane on the floors after I put a coat of sanding sealer. Well he didn’t do a very good job. I’m well aware of how to put poly down and have done a number of floors without coming across this problem.

I’m not interested in instructions on how to put polyurethane down.

I’m looking for advice on what to do to a floor with bubbles on it now. If I put another layer of poly down I asume they will still show Should I sand the layer of poly off completely and start over? Can I sand off the top of the bubbles so the next layer of poly can fill the gap?

You can sand just the bubbled area, and then apply another coat. But you need to re-apply over the whole floor, not just where you sanded. That will sometimes work, though a careful look may show a difference between the areas that have 2 coats vs. the sanded areas with only a single coat. Depends on just how demanding of perfection you are.

If that doesn’t do it, you can always sand the whole floor and start over. (But you will have wasted the time you put into trying to fix it.)