Tons of other leafers could float.
In this video, they drive a few across a pond
https://www.youtube.com/watch?v=uOm_dYs8-78
Technically this is still floating
https://www.youtube.com/watch?v=LwwddWg08Nc
Now as for floating a modern monster truck? According to the 2011 Monster Jam yearbook, "Old School" trucks weighed in at about 15,000 LBS. Obviously with the many different shapes and sizes truck were in those days, we could probably argue that that estimate could give or take about 1,500 LBS, maybe even more. Now, we all know monster trucks weigh 10,000 LBS, but from what drivers have told me, FELD's fleet currently weighs about 12,000 LBS on a CRD, and sometimes about 13,000 LBS on an Inhouse/Cohen chassis where more things have had to be added to keep it up to date. So with weight being an issue I suppose it possible. I won't look into tire pressure because technically you could just inflate the tires more if you planned on doing this. So, in theory, yes, Modern Monster Trucks can float. The real issue comes with how modern trucks are designed notice in those videos how much the trucks using single tires sink in before floating? They can only survive that because in those trucks the engine is really high up above the frame. In a modern truck it would be very likely that the engine would be submerged.