Reading a Lowrance Elite 4 I apologize now for my noobness.

[vincentek9]

dolphin mark and seal mark are pretty similar.
a shark the same size gives a diff mark
a wsb also gives a diff mark (squigly line... worm.. snake...)
a yt gives a very nice arc (especially if you have your chart speed increased)

big floating blobs is usually baitball. sometimes too small to hook

big floating blobs WITH ARCS under/around them... you want to target those arcs. they are big fish chasing the bait ball.