What is the difference between nearsighted and farsighted lenses?

Nearsighted (myopia) lenses use negative SPH values to correct distance vision. Farsighted (hyperopia) lenses use positive SPH values to help with close-up vision.

How do I find the sphere (SPH) value on my prescription?

Look for SPH or Sphere. It can also be labelled Power or PWR. A minus sign (-) is nearsighted and a plus sign (+) is farsighted.

How should I adjust my prescription for clear vision underwater?

For most people, choose 0.50 diopters weaker (towards zero) than your normal SPH, then select the closest available 0.50 step.

I have astigmatism (CYL). What should I choose?

Use your SPH for each eye. The + or minus sign on your CYL matters. Nearsighted: CYL 0.00 to 0.75 go 0.50 weaker. CYL 1.00 to 1.75 minus CYL stay close to SPH up to 0.50 either direction. CYL 1.00 to 1.75 plus CYL stay at SPH or 0.50 weaker. CYL 2.00+ minus CYL stay at SPH. CYL 2.00+ plus CYL stay at SPH. CYL 3.25+ nudges toward SE. Farsighted lenses come in whole steps +1 to +5. Special case: SPH -0.50 or -0.75 with CYL 2.50+ start at -1.00. SPH +0.50 or +0.75 start at +1.00.

I can't find my lens strength in the dropdown. What should I do?

Choose the closest available option. Upload your prescription or email info@oceansoptics.com if you want us to confirm the best match.

Can I choose different lens strengths for each eye?

Yes. You can select different strengths for left and right eye and mix and match any combination available in the dropdown.

How do I upload my prescription during checkout?

On the product page you can optionally upload your prescription. You can also leave a note in the cart or email info@oceansoptics.com.

How do I stop my mask from fogging?

Try the toothpaste trick: rub a small amount on the inside of each lens in circular motions, then rinse. Before each session use a tiny amount of baby shampoo or dish soap, rub a thin film on the lens, then lightly rinse.

Do you have a guide to help me use my mask properly?

Yes. Mask 101 guide: https://cdn.shopify.com/s/files/1/0798/8055/2781/files/Mask_101.pdf?v=1728895468

What happens if I accidentally choose the wrong lens strength?

Message us as soon as possible. If the order has not entered the build or shipping stage yet, we can usually update the lens selection.

Are your lenses safe for both snorkeling and scuba diving?

Yes. Lenses are HD tempered glass and suitable for snorkeling and scuba diving up to 100 ft (30 m).

How long does delivery take, and can I track my order?

Most orders arrive in 5 to 10 days, but allow up to 14 days to be safe. Tracking is provided by email once shipped.

What is your return or exchange policy for prescription masks?

You have 30 days from delivery to request a return as long as the item is unworn, unused, with tags, and in original packaging.

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Rx Obsidian Nearsighted Prescription Snorkel & Scuba Dive Mask

Name: Rx Obsidian Nearsighted Prescription Snorkel & Scuba Dive Mask
Brand: Oceans Optics
SKU: 14:29#Strength -100;200007763:201336100
Price: 70.00 USD
Availability: InStock

Looking for farsighted lenses (+1.0, +2.0, +3.0, +4.0, +5.0)? See Rx Obsidian Farsighted Page

Quantity

$70.00 USD

SALE Sold out

Shipped with Care. No Hidden Fees. Just Clear Vision Ahead.

10% OFF

Use code OCEAN10 at checkout.

Mask Description

The Obsidian Corrective Mask for Nearsighted Adventurers is made for those who want sharp, clear vision underwater without relying on contact lenses.

With precision-crafted tempered glass lenses matched to your prescription, you'll see the ocean as it's meant to be seen.

The soft black silicone skirt fits comfortably on medium-sized faces, forming a secure, watertight seal.

Whether you're snorkeling in shallow reefs or diving deeper, this mask offers dependable comfort, easy equalizing, and excellent visibility.

Designed with performance and style in mind, the Obsidian is your go-to for underwater clarity and confidence.

Prescription Lens Info

Rx Prescription snorkel scuba diving insert Lens

This mask features Myopia/Nearsighted (SPH) lenses in negative diopters, available in increments of 0.50 (e.g. –1.50, –2.00, –2.50). Each lens is made from tempered glass for clarity and safety, and clear underwater vision.

👉 [Not sure which strength to choose? Try our Lens Calculator Tool ›]

Features & Benefits

Corrective lenses built for nearsighted vision (available up to -9.0)

Leak-proof comfort with hypoallergenic soft silicone

Double-seal skirt fits securely on medium face shapes

Wide viewing field to stay aware of your surroundings

Durable materials for both snorkeling and diving

Simple, low-profile buckle system for easy adjustments

Soft nose pocket for quick equalizing

Mask Size Guide

How to measure your face for a prescription mask (width & height)

Rx Obsidian

Size Category: Medium - comfortably fits most face shapes.

How to measure

1 Width: straight line from outer eye corner to outer eye corner (do not wrap).
2 Height: from just under your nose to just above your eyebrow line.

Mask Sizing Ranges

Switch to cm Switch to in

	Min (in)	Max (in)
Width	3.46 ″	5 ″
Height	2.75 ″	4 ″

	Min (cm)	Max (cm)
Width	8.8 cm	12.7 cm
Height	7 cm	10 cm

Options: Nearsighted lenses · Face seal in Black or Clear · Frame colors: Black, Blue, Red, Yellow, Aqua, Pink · Optional action-camera mount.

Hand-Assembled. Free Shipping Over $70

Every Obsidian is made to order. Enjoy FREE USPS tracked delivery when you spend $70 or $5.99 for orders under $70. Shipping takes 5-14 days. (5-10 on average)

30 Day FREE Returns

Take advantage of our FREE 30 days from delivery easy return policy. Shop with confidence. Eligible items only. For more info see our return policy.

More than JUST a Guide!

Snorkelling 101 is Your Ultimate Guide to Better Aquatic Adventures.

Now free with every order! Access your eGuide instantly after checkout or via email, and dive in at your own leisure.

View full details

Man wearing a prescription snorkeling mask with a beach and ocean in the background

Underwater Lens Calculator

Underwater, light bends differently and can make your usual prescription feel too strong. We adjust it slightly for comfortable vision underwater. Enter your prescription to find your recommended underwater lens strength

Sphere Right (OD)

CYL:

Sphere Left (OS)

CYL:

What people are saying about the Rx Obsidian

⭐⭐⭐⭐⭐ Joe, Arizona

"Fantastic! The last time I went snorkeling (more than 10 years ago) I wore contacts. At age 65, glasses only. I thought I was done snorkeling, until I found these! They worked perfectly! | could see the fish. And at around 80 bucks for the mask and a breather tube, it's a bargain.
They charge like $25 to rent them at the beaches when you go on a cruise (and it is gross using something that was in someone else's mouth!) I highly recommend these if you are near-sighted and want to snorkel."
⭐⭐⭐⭐⭐ Allison R, Florida

Prescription goggles
We ordered a pair of prescription goggles for our trip to Hawaii and couldn't be more please with our purchase.
Shipping was quick and they worked great!
⭐⭐⭐⭐⭐ Sage, Utah

"I got the obsidian, my sister got the lumix, we also decided on matching snorkels, and they looked so cute together. We went snorkeling in mexico, and this time was so much less scary since not everything was blurry.
There were also some really cool tips in the snorkeling guide, we found the part about buddy safety and communication especially useful."

The Ultimate Beginners Guide

Included with Every Purchase

Snorkeling 101:

more than JUST a guide

Learn how to set up and use your snorkeling equipment like a pro.
Learn about fascinating marine species and where to find them.
Master the best techniques for keeping your mask clear from water and fog.
Get tips on potential hazards and how to avoid them while enjoying your adventures.

Your Mask Helps Build and Grow a Coral Reef!

When you buy from Oceans Optics, you are not just getting an excellent mask, you are helping us build a real living Coral Reef.

A portion of every sale goes towards our artificial reef project in Koh Tao, Thailand. We worked with Global Reef and the Thai Department of Marine & Coastal Resources to sink a custom steel structure shaped like a prescription scuba mask. Onto this frame we attached living coral fragments that grow over time, attracting fish and turning the structure into a living reef and safe haven for marine life.

So each time you wear your mask, be proud that you are also contributing to saving ocean we all love.

Learn More

Rx Lens Strength + Face Fit

Find Your Prescription Mask Quiz

Built specifically for prescription snorkel and dive masks, this quiz helps match your lens strength, face fit, and intended use in one simple flow.

Answer up to 6 quick questions in about 2 minutes.

Start the quiz →

Have your prescription nearby if you know your numbers. If not, no problem, we can still guide you.

Lens strength Face fit Snorkel or dive

4.94 / 5 based on 1223 verified reviews

Your prescription image is only used to read your values. It is never stored.

How to account for Cylinder?

Find your CYL value below, then check the sign (+ or −) for your recommendation

Nearsighted (Minus −)

Your CYL	Recommendation
0.00 – 0.75	Go 0.50 weaker than your SPH (closer to zero) Example: SPH −3.00 → choose −2.50
1.00 – 1.75	If your CYL shows a − minus sign: stay close to your SPH. You can go up to 0.50 stronger (further from zero) or up to 0.50 weaker (closer to zero) Example: SPH −3.00 → anywhere from −2.50 to −3.50 If your CYL shows a + plus sign: stay close to your SPH. You can go up to 0.50 weaker (closer to zero) or stay at SPH Example: SPH −3.00 → choose −3.00 or −2.50
2.00+	If your CYL shows a − minus sign: stay exactly at your SPH. Only go 0.50 stronger (further from zero) if you specifically want sharper detail and are prepared for more eye strain on longer sessions Example: SPH −3.00 → choose −3.00, or −3.50 for crispness only If your CYL shows a + plus sign: stay exactly at your SPH. Do not go weaker Example: SPH −3.00 → choose −3.00

Special Case: If your SPH is −0.50 or −0.75 and your CYL is 2.50 or higher, we recommend starting at −1.00. Going weaker than this rarely gives useful correction underwater.

Not sure if your CYL is plus or minus? Check your prescription slip. It will show either a − or + sign next to the CYL value. If there is no sign shown, ask your optometrist which form your prescription is written in.