Reels vs. Spools: What’s the Difference?
If you've ever deployed a surface marker buoy (SMB) or seen divers using guidelines underwater, you may have noticed they use either a spool or a reel. While both tools manage underwater lines, they are designed for different purposes.
For most recreational divers, a spool is the better choice—it’s simpler, more reliable, and better suited for typical recreational diving. Reels are larger, more complex, and generally unnecessary unless you're doing specialized dives.
Quick Comparison: Reels vs. Spools
| Feature | Reel | Spool |
|---|---|---|
| Design | Enclosed casing with a handle | Open, circular plate with holes |
| Line Capacity | Usually holds more line (50ft - 400ft) | Typically holds less line (15ft - 150ft) |
| Ease of Use | Requires practice but allows controlled line release | Simple, but requires dexterity to manage tension |
| Deployment | Good for long-distance guideline work | Best for SMB deployment |
| Best For | Wreck/cave diving, search patterns | SMB deployment, short navigation references |
| Risk of Tangling | Lower due to enclosed spool | Higher if mishandled |
| Maintenance | Moving parts require occasional upkeep | Simple design, minimal maintenance |
What Is a Spool?
A spool is a simple, open circular disc with a line wrapped around it. Unlike a reel, it has no handle or locking mechanism—you manually control the tension by holding the edges of the spool.
Best used for:
- SMB deployment – Compact, lightweight, and reliable.
- Short-distance navigation – Simple guideline reference.
Considerations:
- Easier to drop if not handled carefully.
- No tension control—requires a firm grip to prevent line runaway.
For nearly all recreational divers, a spool is the best option—it’s small, simple, and has fewer failure points.
What Is a Reel?
A reel consists of a casing with a handle and a spool of line inside, controlled by a thumb-operated tension knob or locking mechanism. Some models have a spring-loaded ratchet to prevent free-spooling.
Best used for:
- Cave diving & wreck penetration – Enables precise line laying.
- Technical diving – Preferred for long distances.
- Search & recovery diving – Allows controlled search patterns.
Why Recreational Divers Rarely Need a Reel:
- No need for guideline laying in standard open-water dives.
- Reels have more moving parts, which means more chances of failure (e.g., jamming, tangled line).
- Bulkier and less convenient compared to a simple spool.
Unless you’re trained in wreck penetration, technical diving, or specialized search & recovery, a reel is unnecessary for recreational diving.
Spool Material Choices & Why It Matters
Not all spools are created equal. The material affects durability, weight, grip, and reliability.
| Material | Pros | Cons |
|---|---|---|
| Delrin |
- Durable and impact-resistant - Sinks slowly, reducing loss risk - Some models come in multiple sizes and can be outfitted with a cold water/dryglove handle |
- More expensive than plastic - Slightly heavier than plastic |
| Plastic (ABS, Nylon, etc.) |
- Lightweight - Inexpensive - Won’t corrode |
- More brittle—can crack on impact - Can feel slippery, especially in cold water |
| Aluminum | - Strong and resistant to breaking |
- Sinks very fast if dropped - Can corrode if not properly anodized - Sharp edges if poorly machined |
Why Delrin Is a Good Choice for Most Divers
- Durability & Strength: Holds up better than plastic, doesn’t crack as easily when dropped.
- Sinks Slowly: Unlike aluminum, which sinks fast, Delrin gives you a better chance to recover it if dropped.
Other Considerations
- Some Delrin spools, like Halcyon’s, offer multiple sizes and the option for a cold water/dryglove handle.
- Plastic spools are fine for occasional recreational divers who just need a basic option for rare SMB deployments.
- Aluminum spools are not ideal unless you’re okay with the risk of losing one if dropped.
Bottom Line: If you want a durable, reliable spool, Delrin is a solid choice
SMB Use & Spool Setup
I always carry an SMB with a spool attached on every dive—it’s a basic safety tool that every diver should have.
If I’m doing anything more than a fun dive, I also carry a backup spool in my right pocket as a redundancy in case I need additional line.
Should You Carry Both?
- Recreational Divers: A spool is all you need for SMB deployment.
- Technical Divers: May carry both—a reel for penetration and a spool as a backup.
For 99% of recreational divers, a spool is the right tool, and a reel is overkill.
Final Thoughts
If you're a recreational diver looking for the best way to deploy an SMB, get a spool. It’s simpler, more reliable, and fits all recreational diving needs.