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C-420 Marathon 21 Dual-Temp

C-420 Marathon 21 Dual-Temp

A premium above-ground swim spa with 46 therapy jets and a designated spa zone with 6 seats. 
MSRP: $52,499
$33,599
Save $18,900
ADDITIONAL COUPON SAVINGS
Save an extra $1900-$4000
Labor Day Sale – Ends 9/7
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MSRP: $52,499
$36,999
Save $15,500
In-house financing
100% approval rate
Special Financing
60 months 0% interest*
Labor Day Sale – Ends 9/7
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*60 months no-interest financing available to well-qualified buyers.

Manufacturer’s instant rebate & sale coupon are only available to cash/credit card buyers.

Standard Features

  • Above-Ground Swim Spa: An above-ground swim spa with therapy seating and a swim lane.
  • 3 Jets: Equipped with 3 river jets for continuous swimming.
  • Touchscreen Controls: The user-friendly touchscreen interface provides intuitive control of swim spa and hot tub functions.
  • Multi-Layered Fiberglass Reinforcement: Reinforced fiberglass construction ensures superior strength and long-term durability.
  • Heat Flow Manifolds: Efficient system captures and distributes warmth for improved performance.
  • Insulated Cover: Energy-efficient cover helps retain heat and protect the spa.
  • 100% Anti-Fungicide Plumbing: Prevents bacterial buildup for cleaner water and reduced chemical use.
  • ABS Bottom Protection: Protects against moisture, pests, and ground contact.
  • Catalina Skirting: Durable exterior skirting with a refined finish.
  • Integrated Energy Efficient Technology: Maximizes performance while reducing operating costs.
  • Made in the USA: Crafted with quality materials and trusted workmanship.

Swim Side

  • 46 Therapy Jets: Equipped with 46 powerful hydrotherapy jets.
  • Premium Lighting Package: Includes underwater, perimeter, fountain, and waterfall lighting.
  • 8 LED Side Lights: Enhances visibility and ambiance.
  • 4 LED Step Lights: Improves safety and visual appeal.
  • 24 LED Perimeter Lights: Creates a full glowing perimeter effect.
  • Standing Body Massager: Targeted full-body hydrotherapy station.
  • 3 Stainless Exercise Rails: Provides stability for workouts.
  • Ceramic Swim Lane & Water Line Tile: Elegant, durable tile finish.
  • LED Backlit Jets: Illuminated jets for visual impact and therapy performance.
  • UV Sanitation System: Improves water purification and clarity.
  • ClearView H-500 Ozonator: Enhances water quality and reduces chemical use.
  • 100 Sq. Ft. High-Performance Filtration: Large-capacity system ensures clean water.

Spa Side

  • Six Therapy Seats: Ergonomic seating for up to 6 people.
  • 57 Jets: Powerful hydrotherapy jet system.
  • Premium Lighting Package: Includes underwater, perimeter, and fountain lighting.
  • Neck, Shoulder, Calf & Foot Jets: Full-body targeted hydrotherapy.
  • WiFi Connectivity: Remote monitoring and spa control.
  • UV Sanitation System: Maintains cleaner, healthier water.
  • H-100 Ozonator: Enhances water purification and clarity.
  • Bluetooth Water-Resistant Audio System: Built-in speakers and subwoofer for immersive sound.
  • LED Backlit Jets: Adds visual ambiance and therapeutic effect.
  • 2 LED Cabinet Accent Lights (End Panels): Enhances exterior design and visibility.
  • 100 Sq. Ft. High-Performance Filtration: Ensures crystal-clear water on spa side.

Available Upgrades

  • AnyTemp® Hot and Cold Spa System
  • Swim Pole & Harness System
  • (3-Pack) CopPure Filters
  • Swim Spa Steps
  • Spa Booster Seat
  • Fresh Water Mist System
  • Spa Startup Chemical Kit
  • (3-Pack) Nature2 Spa Water Purifier
  • Rechargeable Floating Drink Station
  • Row Kit:
    • Includes a rowing kit
    • Two resistance bands for arms (2)
    • Two resistance bands for legs (2)
    • Attach at the wrists and ankles

Product Information

Technology

Product Highlights

FAQs

Frequently asked questions

A swim spa is a long, rectangular spa that combines the swimming benefits of a pool with the hydrotherapy and convenience of a hot tub. A powerful current at one end lets you swim continuously in place — no wall to flip off, no laps to count — while the other end functions as a traditional hot tub with jets and seating. Swim spas are popular because they deliver year-round swimming, fitness, hydrotherapy, and recovery in a fraction of a pool’s footprint and cost.
A swim spa offers most of what a pool does at a fraction of the cost, footprint, and maintenance burden. Pools require excavation, permits, decking, separate heaters, and seasonal opening and closing. A swim spa installs above-ground in a fraction of the time, runs year-round (including in cold climates), uses far less water, and combines swimming, hydrotherapy, and hot tub functions in a single unit. For most homeowners, a swim spa delivers the lifestyle benefits of a pool without the ownership burden.
Whisper Outdoor swim spas typically range from around $15,000 for compact single-zone models to $30,000+ for premium dual-zone units with full swim currents, hydrotherapy seats, and cold-zone capability. Because we manufacture our swim spas in Tennessee and sell factory-direct through our own showrooms, our pricing typically runs significantly below comparably equipped swim spas sold through traditional dealer networks. Most swim spa buyers finance through one of our three financing paths to spread the cost into manageable monthly payments.
Yes — and that’s one of the main reasons people choose swim spas over pools. Swim spas are insulated, heated, and built for year-round use in any climate. The water stays at your preferred temperature 365 days a year, so you can swim, do hydrotherapy, or relax whether it’s 90 degrees or below freezing outside. Many owners report using their swim spa more often in winter than summer.
Swim spas typically range from about 12 feet to 21 feet in length. Shorter models (12–14 ft) are ideal for fitness swimming, hydrotherapy, and households with limited space. Mid-size models (14–17 ft) offer more swim distance and often include separate hot tub seating. Larger dual-zone models (17–19+ ft) feature a dedicated swim zone and a separate hot tub zone, ideal for households who want a complete wellness solution.
Every Whisper Outdoor swim spa is designed and manufactured in Tennessee, USA — in the same facilities where we build our hot tubs, golf carts, and UTVs. American materials, American labor, and direct factory oversight on every unit. Building in-house gives us complete control over quality and means warranty service goes directly through the manufacturer, not a third-party dealer.
Swim spa delivery is more involved than a hot tub but far simpler than building a pool. Most swim spas install above-ground on a level concrete pad, deck, or properly prepared base — no excavation required. Our team coordinates delivery directly to your home, and your local Whisper Outdoor showroom can help connect you with installation resources in your area. A licensed electrician will be needed for the 220V hookup; the rest is typically straightforward.
Because swim spas are a larger purchase, our extended financing terms make a meaningful difference. We offer three financing paths: in-house financing with a 100% approval rate and terms up to 84 months — meaningful for higher-ticket purchases — plus third-party financing through Wells Fargo and promotional 0% APR offers when available. Most applicants receive a decision within 1 business day of applying online.

Exclusive savings awaits

Save up to $4000 during our Labor Day Sale.

Special financing for all credit types — low monthly payments, easy approvals. Get your personalized savings sent straight to your inbox.

Get your exclusive Savings

Resort-level wellness, factory-direct pricing.

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Exclusive savings awaits

Save up to $4800 during our Labor Day Sale.

Special financing for all credit types — low monthly payments, easy approvals. Get your personalized savings sent straight to your inbox.

Get your exclusive Savings

Your next day on the water starts here. 

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Exclusive savings awaits

Save up to $2300 during our Labor Day Sale.
Special financing for all credit types — low monthly payments, easy approvals. Get your personalized savings sent straight to your inbox.

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Exclusive savings awaits

Save up to $5000 during our Labor Day Sale.

Special financing for all credit types — low monthly payments, easy approvals. Get your personalized savings sent straight to your inbox.

Get your exclusive Savings

A few seconds – and your exclusive savings are on the way.

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