The short answer: buy the Blackfinunless you specifically want a glass lens or the Blackfin is too big for your face. Both frames are wrapped nylon, both carry Costa’s polarized 580 lens, and both state 100% UV protection, so the badge and the glare control are a wash. What differs is how much of your face the frame covers and — in the versions actually on sale — what the lens is made of. The Blackfin is the larger frame with the lighter, tougher polycarbonate lens, and for most people that is two wins.
The reason this comparison is more confusing than it should be is that you are not making one decision. The Fantail we carry is the 580G glass trim; the Blackfin is the 580P polycarbonatetrim. So “Fantail or Blackfin” is really “moderate frame with a glass lens, or large frame with a plastic one,” and the material half of that question has a much bigger effect on your day than the shape half does. We have separated the two below, and if the material is your real question our 580G vs 580P comparison is the page that only deals with that.
What is the same on both
Worth clearing out of the way, because it is most of the product.
- Polarization.Both are polarized, and across Costa’s 580 range that is standard rather than a paid upgrade on selected SKUs — one of the few premium brands where you do not have to check. The AAO describes polarization as the feature that addresses reflected daytime glare, which on water is the whole point.
- UV.Both listings state 100% UV protection. The FDA’s own device page treats ultraviolet blocking and light transmittance as separate measurements against ANSI Z80.3 and ISO 8980-3, so a stated UV figure is the one you want and it is present on both.
- The 580 tint idea.Both use Costa’s 580 lens family, which filters a specific band of light to raise contrast. That is what people are buying when they buy Costa, and it is common to the two frames.
- Frame material and warranty terms.Both are bio-based nylon, and both fall under the same warranty: Costa’s care and repair page gives a two-year limited warranty on non-prescription sunglasses bought on or after 3 November 2022, and explicitly classes scratched lenses, broken hinges and accidental damage as out-of-warranty damage handled by a paid repair programme. Neither frame protects you from the cost of dropping it.
What actually differs
1. Coverage, and whether your face can take it
The Blackfin is the bigger, squarer, more enveloping frame, with a 62mm lens and a shape built to block light arriving from the side on open water. The AAO’s frame guidance is explicitly geometric — it recommends wraparound and oversized frames so that light cannot reach the eye around the lens — so the larger frame is genuinely the better protector of the two, not just the bolder one.
The cost is fit. A large square wrap on a narrow face sits on the cheekbones and looks borrowed, and that is the single most common complaint about this frame. The Fantail is the moderate option: still wrapped, still a fishing frame, less of it. If your sunglasses normally look slightly too big, that is your answer between these two, and our small-faces roundup deals with the problem in general. If the opposite is true, our big-heads roundup is the page, and the Blackfin is the better starting point.
2. Glass or polycarbonate — the decision that matters more
This is where the real difference lives. Glass is optically clearer and far more scratch resistant; polycarbonate is far lighter and far more impact resistant. Neither is better in the abstract and the choice follows the use.
Glass winsif you are sight fishing — staring into water for hours looking for shapes — and if your sunglasses live in an environment that scratches plastic, which a boat is. Costa’s own warranty terms treating scratches as out-of-warranty damage is a quiet argument in the same direction.
Polycarbonate winson weight over a long day, on impact safety, and on anything where the glasses might be dropped onto a hard deck. Prevent Blindness’s point that ordinary sunglasses are not sports eye protectors still applies — neither of these is protective equipment — but a brittle lens is the worse of the two to have on your face when something goes wrong. It is also substantially cheaper.
For a full day of mixed activity, polycarbonate. For a specialist sight-fishing lens, glass. Our glass vs polycarbonate guide covers the trade across the whole market rather than inside one brand.
3. Weight on a long day
Neither listing publishes a gram figure, so we are not going to invent one. What is not in dispute is the direction: a glass lens in a wrapped frame is meaningfully heavier than the same frame in polycarbonate, and the weight is carried on your nose bridge. On a four-hour outing it is irrelevant; on a twelve-hour day in the sun it is the thing that decides whether the glasses end up on your hat.
4. Price
Both are premium and the glass trim is the dearer of the two. Live prices for both are on the cards below with the date they were read. The gap is real money, and it buys you scratch resistance and optical clarity rather than more glare control — the polarization is identical.
Which to buy
- Sight fishing, flats, staring into water: Fantail 580G. This is the case the glass lens was made for.
- Long boat days, open water, bright sun: Blackfin 580P. Bigger coverage, lighter on the nose, tougher if it lands on a deck.
- One pair for fishing, driving and everyday: Blackfin 580P. Polycarbonate is the right lens for a frame that leaves the boat.
- A narrow or smaller face: Fantail. The Blackfin will be too much frame regardless of which lens you prefer.
- You are not sure Costa is the right brand: read Costa vs Maui Jim or Costa vs Oakley first. Choosing between two frames in a range you have not committed to is the wrong order to do this in.
The two frames in full
Ranked for the buyer described above rather than on absolute lens quality — on lens quality alone the glass wins and costs more. Every spec is read from the product’s own listing on the dated visit shown on its card, prices are pulled live, and we have not field-tested either of these.
#1Best for most buyers
Costa Del Mar Blackfin 580P
Costa's wraparound answer to bright, open water. The Blackfin's 62mm front curves further round the temple than the Fantail, which cuts the side light that sneaks in when the sun is low and you are looking across a flat surface. The 580P lens keeps it light enough to wear from launch to loading the boat.
Strengths
- +Wrapped 62mm front blocks low-angle light from the side
- +580P polarized polycarbonate — light and impact-resistant
- +Blocks 100% UV; integral hinges built for salt exposure
Trade-offs
- −The wrap looks unmistakably like fishing eyewear off the water
- −580P is softer than glass and picks up scratches faster
| Lens feature | 580P polarized wrap, 62mm coverage, 100% UV |
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| Polarized | Yes |
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| Lens tint | Not published |
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| Frame material | Bio-based nylon |
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| UV protection | 100% UV protection |
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| Best for | Fishing, Boating, Beach, Wide faces |
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Spec note. Amazon lists this Blackfin as a 62mm polarized 580P frame; 580P is Costa's polycarbonate lens, lighter and more impact-resistant than the 580G glass version of the same contrast tint.
Specs read from the product listing, on August 10, 2026. “Not published” means the brand does not state that figure.
#2Best lens, for the angler who wants glass
Costa Del Mar Fantail 580G
If you fish, this is the benchmark. Costa's 580G glass lens is polarized, scratch-resistant and cuts the yellow wavelength to sharpen contrast on the water — so you see structure and fish, not surface glare. Glass costs more and weighs more than polycarbonate, but the optical clarity is the reason anglers pay it.
Strengths
- +580G glass lens is polarized and exceptionally scratch-resistant
- +Cuts glare and sharpens contrast on and under the water
- +Blocks 100% UV; encapsulated mirror survives salt and spray
Trade-offs
- −Glass lens is heavier than polycarbonate
- −Premium price — the most expensive way to see fish
| Lens feature | 580G polarized glass, glare-cutting tint, 100% UV |
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| Polarized | Yes |
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| Lens tint | Gray / copper (580G, varies) |
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| Frame material | Bio-based nylon |
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| UV protection | 100% UV protection |
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| Best for | Fishing, Boating, Bright water |
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Spec note. Costa's 580 lenses filter high-energy yellow light to boost contrast; the 580G variant is glass (vs. 580P polycarbonate) for maximum scratch resistance and clarity.
Specs read from the product listing, on July 18, 2026. “Not published” means the brand does not state that figure.
And if neither is the answer
Both of these are three-figure frames, and the honest thing to say on a page like this is that the specs that matter most — polarization and a stated UV rating — are available for about a tenth of the money. What you get for the premium is lens refinement, build and a warranty programme, which is a real purchase but not a protective one. Our fishing roundup ranks both of these against budget pairs, and are expensive sunglasses worth it takes the general version of the question apart. If the Costa lens is what you want but the frame size is the obstacle, the brand review covers the rest of the range.