“You are standing on the shore of Lake Manchar. You spot a tasty fish swimming some distance below the lake surface.(a) If you want to spear...

Refraction in this case is referring to the fact that when
a beam of light goes from a substance of one density to a substance of another density
the speed of light changes and a beam of light will bend.  To determine which way the
light ray will bend, draw a normal line to the interface of the two different
substances.  In other words, a line perpendicular to the
surface.

If the beam of light - your laser or light
reflected fish's body - is going from air to water, the density of the water is greater
than that of air and the ray will bend toward the normal line.  That means it will bend
down toward the bottom of the water.

Because of this
bending the fish will appear closer to you than it actually is so you need to aim
farther out than where the fish appears to be.  How much farther out depends on the
angle at which you are looking at the fish. If you are looking straight down there is no
bending, but as the angle of your eye away from the normal increases the more you will
have to adjust your aim.

Note:  it does not matter if you
are throwing a spear or using a laser. In both cases, the light is bent (refracted)
going from one medium to another.  You probably will not be able to cook your fish
underwater with your laser. With the high heat capacity of the water, it would be
difficult, if not impossible, to actually cook the fish.