The ULTRAMARINE is the result of four
years of research and development,
conducted by Extrema Ratio in
collaboration with Military Dive Teams of
the Italian Special Forces, Law
Enforcement Dive Teams and Civilian
Underwater Operation Experts.
Units involved in underwater and amphibian operations use a variety of specialty
tools. The main objective of the ULTRAMARINE Project is to substitute these
different tools with one versatile utensil capable of performing the multitude of tasks
that professionals in the fields are asked to perform in these difficult and
The Primary Functions are:
1. FIELD OPERATION
2. UNDERWATER OPERATION
3. EMERGENCY TOOL
Note: Functions are prioritized by frequency of use in each sector.
1. Field Operations:
• As with any respectable working tool, the mass of the blade has to be heavy
enough to efficiently chop branches and shrubs in order to make emergency
shelters, camouflage emplacements, stretchers, utensils or sector stakes.
• The serrations facilitate cutting rope when the blade is dull from wear & tear.
• The steel tang can be used as a hammer or glass breaking tool.
• The sharp portion of the blade near the handle can be used for precision
cutting & whittling.
2. Underwater Operations:
The slot in the blade was
developed for use as a
To avoid damaging buoyancy or wrench.
flotation devices during on-
board operations with the
exposed metal components of
the knife, a flap was
incorporated to cover the
sheath & knife.
The retention lanyard allows the
user to work on equipment
without having to sheath the
• The handle was designed with a plus sized grip & a special anti-slip
material developed by Extrema Ratio to facilitate retention while
wearing neoprene gloves.
• With load positioned
on the weakest end of
the line cutter the
blade withstands a
load index of 45 kg
• On the blade with screw -
pin shackle wrench slot,
with load positioned in the
center, the blade
withstands a load index of
70 kg (154 lbs).
• On the blade without screw-pin shackle wrench slot, with load
positioned in the center, the blade withstands a load index of 180 kg
3. Emergency Tool:
• The sheath is designed to be sleek and
hydrodynamic, with a close, tight fit to
the body that reduces the possibility of
• The sheath also has a quick-release
function that allows the knife to be
rapidly drawn by simply pulling on the
upper portion of the protective flap.
• The protective flap uses special anti-wet
snap fasteners that are specifically
designed for water environments.
• O-ring and retention system are
disabled with a strong pull.
• In panic or shock situations the user
will have access to the knife.
Emergency Tool continued:
• The knife is designed with a specialized net & line cutting
system for use in entanglement emergencies.
• The knife is designed with reduced hilt guards to reduce the
chance of entanglement and snaring while in use.
Emergency Tool continued:
• The design of the handle allows the operator to distinguish the
orientation of the blade by feel in low light / no light situations.
• The pointed tang was developed as a glass break device.
• Besides being a good camp knife the ULTRAMARINE was
designed so the handle could be disassembled, the blade
attached to a pole and used as a spear.
• The blade has been
treated with a matt finish
to reduce light reflection
wile operating in hostile
• The sheath incorporates
two sharpening diamond
sharpening plates: one for
the primary blade and the
second for the net cutter.
• The symmetric dagger shape
of the blade and a balance
point biased toward the handle
make the ULTRAMARINE an
excellent fighting knife.
• The pointed steel tang can be
used as a blunt force weapon.
The hard sheath combined with a sleek design make the
ULTRAMARINE a safe and effective solution for use in
airborne operations, which eliminates the issues of mid-air
entanglements, towed jumpers and operator impalement.
The ULTRAMARINE was conceived as a multi use,
amphibian knife. As such it needs to rapidly and easily
transition from the operators waterborne equipment to his
field tactical gear. To meet this requirement Extrema Ratio
developed two separate sheaths:
• The Dive Sheath
• The Field Sheath
• The Dive Sheath is a rigid sheath made of ABS plastic
which can be worn on the ankle or mounted to
equipment webbing with a TEK-LOK fastener.
• The optional Field Sheath
is M.OL.L.E. system
compatible and can be
attached to a variety of
field and tactical
Waterborne operations, in particular
saltwater ops, place inordinate
amounts of wear on operational
equipment. To alleviate this problem
the ULTRAMARINE was developed
using new concepts and materials that
guarantee the durability of the utensil.
The philosophy behind the
ULTRAMARINE Project is not to
attract the potential buyer with the use
of exotic or futuristic materials and
applications, but to develop a
functional and durable tool made out of
carefully selected and extensively
• The sheath is composed of two detachable parts:
1- The soft part is made of polyamide bonded with polyethylene.
2- The hard part in ABS plastic welded together with a
specialized binary epoxy.
• The elastic straps are doubled.
• Accessories are made of polyamide.
• The snap fasteners are specifically designed for wet environments.
The handle is a single cylindrical block of polyamide.
The tang and other components are stainless steel.
The blade is made of Cobalt Steel N690: This steel is
certified by Extrema Ratio to pass all oxidation tests under
N.A.T.O testing standards.
• Stainless Steel is subdivided into three families:
• Austensistic and Ferritic have the highest levels of oxidation reistance,
but are not hardenable by heat treatment. A certain level of Rockwell
Hardness (HRC) is necessary for edge retention and the production of a
long lasting blade.
• Martinsistic Steel has a good level of corrosion resistance, especially
when it contains high levels of Chrome (min 12%, N690 contains 17%),
and can be readily tempered.
• Martinsistic Steel needs same level of maintenance of portable
weapons in underwater environment.
The EOD version is available upon request. In the EOD
model all steel components are replaced with Titanium
components that have a neglegible magnetic mass.
This version is recommended only for EOD use because
even though Extrema Ratio uses only the highest grade of
titanium (Grade 5 @ 40 HRC), this metal is still a fairly soft
alloy that is difficult to sharpen and does not hold and edge
• Most military knives use a factory treated coating such as
Teflon to dull and protect the blade from oxidation. The
problem with this method is that when the protective coating
gets scratched or worn with use leaving the raw metal
exposed to the environment and to oxidation.
• Commercial dive knives us a highly polished finish to protect
the blades from oxidation.
• Neither of these options is suitable for the ULTRAMARINE
knife, so Extrema Ratio decided to adopt a renewable
protective film called LUBRA-SKIN. This coating can be easily
reapplied during regular knife maintenance.
LUBRA-SKIN is a silicone based product specifically
developed for Extrema Ratio. This spray is easily applied
to all disassembled steel parts and creates a waterproof
protective film which prevents salt water from adhering to
the metal and causing oxidation.
• For ease of maintenance the knife handle can be
disassembled without the use of tools.
• Simply rinsing the knife in fresh water is sufficient to prevent
• The inside of the sheath is smooth for easy rinsing and to
prevent salt deposits from sticking to the sheath and being
pressed against the blade.
• For additional wear and tear
most components can be
disassembled and replaced.
• The O-ring can easily be
disassembled and substituted.
• Spare components are
provided as part of a standard
• The female threading inside the handle
is subject to oxidation but is not fixed
and can easily be substituted.
Total length: mm 298
Blade length: mm 150
Blade thickness: mm 6,3
Overall length (knife in sheath): mm 320
Overall thickness (knife in sheath): mm 55
Sheath weight: g 280
Knife w/o screw-pin shackle wrench slot: g 390
Knife with screw-pin shackle wrench slot: g 375
Blade steel: Bohler N690, X105CrCoMo182
(EOD version titanium grade 5)
Metal parts and screws: AISI 303,AISI 304 e
Handle: Polyamide (Nylon)
Hard sheath: ABS
Soft sheath: Cordura, polyamide, polyethylene
foam, accessories in polyamide.