After the autopsy of the young man fished out of the water, the M.E pointed out to CSI Wolfe the gunshot wound on the left of the victim's chest. However, the victim was shot on his right chest during the flashback scene.
While their bites are serious, bull sharks don't prey on humans; they're only interested in wounded fish. Most bites are suffered by spear fishermen. A bull shark smelling blood may bite a swimmer by mistake, but would never feed on a person.
The woman was taken under by a shark, and then her brother dived in. Soon after there was a big turbulence on top of the water that appeared to contain blood. Wouldn't get a big bubble like that in real life. There would be a slow show of blood.
At one point Horatio says about the criminals, "We do have one advantage, they don't know that we are on to them yet." The next scene shows Horatio telling everything he knows to one of the criminals, immediately giving away that advantage.