In order to shoot proper images of the tiniest critters, even a good macro lens can easily reach its limits. When it comes to serious magnification, a close-up lens can deliver. Standard values are usually +5 and +10 diopters, sometimes with the option to stack several close-up lenses.
The UCL-90PRO and the UCL-09PRO by AOI are depth-rated to 60m (200ft) and provide a magnification of +18.5 diopters (UCL-90PRO) or +12.5 diopters (UCL-09PRO).