Partial from MineCraft decompiled source - `EntityFishHook::onUpdate()`

EntityFishHook.java

if (this.ticksCatchable > 0)
{
    --this.ticksCatchable;
}
else
{
    short var28 = 500;

    if (this.worldObj.canLightningStrikeAt(MathHelper.floor_double(this.posX), MathHelper.floor_double(this.posY) + 1, MathHelper.floor_double(this.posZ)))
    {
        var28 = 300;
    }

    if (this.rand.nextInt(var28) == 0)
    {
        this.ticksCatchable = this.rand.nextInt(30) + 10;
    	
    	// ... Play splashing sounds and particles
    }
}