Thanks this baffles me
JesserGood morning, Jesser.
There's water throughout this dream, which always points to emotion. When the friend and you are on the boat together, this points toward the relationship you have with this person. The relationship halted, like the boat, so you ended it. The friend drinks a cup of water (consuming the emotions), then throws ice - frozen water, indication emotions gone cold and hard. This is a conflicting emotional situation, so your confusion is not surprising in the least.
I think it's possible that you feel sad about yourself because you blame yourself for the friendship's end. You were steering the boat when it stopped, you made the decision to dock.