Product Description
The Benchmade Water Collection Undercurrent Serrated (BM18040S) is a hard-use, full-sized fixed blade engineered for hard-cutting marine utility, line slicing, and emergency water rescue. Built to thrive under constant exposure to salt water, this 5.38 oz full-tang knife pairs a partially serrated 4.32" CPM-MagnaCut Sheepsfoot blade with a high-grip Depth Blue Santoprene handle and a Sonar Gray molded polymer sheath.
CPM-MagnaCut Stainless Steel is Crucible's revolutionary powder metallurgy steel engineered to offer unmatched toughness, edge retention, and extreme corrosion resistance in saltwater environments. Hardened to 60–62 HRC, the 4.32" Sheepsfoot blade features a clean Satin finish and SelectEdge® geometry, while aggressive partial serrations near the heel easily slice through heavy rope, netting, and monofilament line.
- Blade: 4.32" CPM-MagnaCut Sheepsfoot with Partially Serrated edge, Flat grind, Satin finish, SelectEdge® geometry, 0.120" thick.
- Handle: Depth Blue Santoprene rubberized scales over full-tang CPM-MagnaCut steel; Textured grip; 5.10" handle, 5.38 oz (knife only).
- Deployment + Lock: Fixed blade knife; No locking mechanism.
- Carry: Sonar Gray molded polymer sheath with push-button release clip included; 9.42" overall length.
Ideal for: commercial fishermen, mariners, watercraft operators, rescue divers, and outdoor adventurers requiring a rustproof, hard-use serrated marine fixed blade.
The Benchmade Water Collection Undercurrent Serrated in CPM-MagnaCut with Depth Blue Santoprene (BM18040S) ships same or next business day from Columbia, Louisiana. Knifeworks is an authorized Benchmade dealer.
Benchmade Undercurrent Serrated: Frequently Asked Questions
Answers to the most common questions about the Benchmade Water Collection Undercurrent Serrated (BM18040S).
What makes the Benchmade Undercurrent BM18040S saltwater proof?＋
The Undercurrent BM18040S features CPM-MagnaCut stainless steel—engineered specifically for extreme corrosion resistance—paired with a molded Santoprene rubber handle and a polymer sheath that will not rust or degrade when exposed to salt water.
Why use a Sheepsfoot blade profile with partial serrations on a marine knife?＋
The straight edge of a Sheepsfoot blade allows for full-length contact during flat slicing cuts, while the blunt tip minimizes accidental punctures to inflatable craft or gear. The serrated heel provides instant cutting power through heavy rope, netting, and cordage.
What sheath comes with the Benchmade Undercurrent BM18040S?＋
The Undercurrent includes a Sonar Gray molded polymer sheath featuring a push-button retention release clip for secure mounting on belts, gear straps, or life jackets.
Where is the Benchmade BM18040S made, and what warranty covers it?＋
The Benchmade Undercurrent is proudly made in Oregon City, Oregon, USA. Benchmade backs the knife with a Limited Lifetime Warranty and free LifeSharp lifetime tuning and sharpening service. Knifeworks does not warranty this product independently.
CPM-MAGNACUT STEEL · DEPTH BLUE SANTOPRENE · WATER COLLECTION
The USA-Made Corrosion-Proof Hard-Use Marine Knife
A 5.38 oz marine fixed blade featuring a 4.32" CPM-MagnaCut partially serrated Sheepsfoot blade, Depth Blue Santoprene handle, and Sonar Gray polymer sheath. Questions? Our team carries these knives daily. We ship same or next business day from Columbia, Louisiana.
Call 888-225-9775
Warranty Information
Benchmade Warranty: Benchmade warrants that its genuine products are free from defects in material and workmanship for the life of the product. The warranty does not cover normal wear and tear, rust, accidents, misuse, improper maintenance, or alterations. Benchmade offers free lifetime LifeSharp services for sharpening and inspection. Contact Benchmade directly for warranty and LifeSharp support. Knifeworks does not warranty this product independently.Specifications
| Product Type | Fixed Blade | |
| Brand | Benchmade | |
| Product Name | Undercurrent | |
| Model # | BM18040S | |
| Overall Length (in) | 9.44 | |
| Blade Length (in) | 4.32 | |
| Handle Length (in) | 4.89 | |
| Blade Thickness (in) | 0.12 | |
| Handle Thickness (in) | 0.84 | |
| Blade Material | CPM-MagnaCut | |
| Blade Hardness (HRC) | 60-62 | |
| Blade Style | Sheepsfoot | |
| Blade Edge | Partially Serrated | |
| Blade Grind | Flat | |
| Blade Finish | Stonewashed | |
| Handle Material | Santoprene | |
| Handle Color | Depth Blue | |
| Sheath Material | Polymer | |
| Sheath Color | Sonar Gray | |
| Weight (oz) | 5.38 | |
| Origin | USA | |
| Blade Range | 4-4.99 |
