This morning I came upon two bulls together at sunrise. (see next image)
They were about to depart so I gave my best cow-moose-in-heat call and caught the attention of this young bull.
For the next hour I called as he worked his way along the far shoreline until he was directly opposite me.
I must have been convincing as he suddenly entered the water and swam towards me with a purpose.
I let him get halfway before stepping out from cover and revealing myself.
He stopped, stared at me for a few seconds, then turned, swam back and disappeared into the forest.

See next image for a view of the two bulls together.