Not All Magnifying Glasses Will Spot Critters

You've seen all the big fish, so for your next dive trips, you want to focus on macro and super-macro marine life . But to enjoy the very colorful but typically tiny creatures that your dive guide will search out and point to, you may need the help of a magnifying glass .

Light is refracted when it passes from a dense medium (the water) to a less dense medium (the air in your mask), making things look larger or closer . But when light passes from a less dense medium (the water) through a more dense medium (the glass in a magnifying glass), the opposite happens, counteracting the effect of the convex lens' curved surface .

The result: A magnifying glass is apparently less effective in water than it is in air . Which means, to see macro life, a good one will have to have at least a 10x magnification in air . Taking that magnifying glass you use to read any fine print (which probably has a magnification ratio of around 4x) will only lead to disappointment.

If you want something conventional with a handle, Amazon has a few inexpensive products in the 10x magnification category . Avoid anything with a built-in light (many of the more powerful glasses come with this feature) . One we like is the Insten 10x Handheld Magnifying Glass with Handle, available for $8 (https://insten.com).