Will a pontoon boat float in a foot of water?

It depends on the mass of the boat. The mass of water displaced by the boat will equal the mass of the boat.

Well, yes that is true, but it doesn't really answer the question so much as explains why the answer for most pontoon boats is "No- it won't". Consider the general rule for boating:

10 feet water, watch out for rocks.

8 feet of water, don't go more than 5 miles per hour.

6 feet of water, idle motor.

4 feet of water is only safe for docking .

2 feet of water, you'll be beached.

0 feet of water, well, that's obvious.