I saw lots of debate about this question. Some are saying that this cannot be solved because the weight of the tubes is not given. Others say the red one experiences more buoyant force because for red: buoyant force=W while for blue: buoyant force+normal force=W. There are also people saying that blue experiences more buoyant force because it displaces more water than red. Can someone please explain which one is correct? Thanks.
2 Answers
https://en.wikipedia.org/wiki/Buoyancy
From the first paragraph: "[The buoyancy force]... is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the displaced fluid."
And the weight of the displaced fluid is entirely determined by the displaced volume...
If the two tubes are identical (except for the weight) and the red one is floating with some of it extending above the fluid surface, then the blue one is displacing more fluid and experiences a greater buoyant force.