/* quick reset */
* {
  margin: 0;
  padding: 0;
  border: 0;
}

/* relevant styles */
.img__wrap {
  position: relative;
  height: 200px;
  width: 257px;
}

.img__description {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  background: rgba(29, 106, 154, 0.72);
  color: #fff;
  visibility: hidden;
  opacity: 0;

  /* transition effect. not necessary */
  transition: opacity .2s, visibility .2s;
}

.img__wrap:hover .img__description {
  visibility: visible;
  opacity: 1;
}