Can Silverfish Swim? Water and Silverfish Explained

Silverfish have a strong association with water and moisture, which leads many people to wonder whether these insects can actually swim. The short answer is no — silverfish cannot swim in any meaningful sense. But the full story of their relationship with water is more nuanced.

Can Silverfish Swim?

No, silverfish cannot swim. They lack the anatomical adaptations needed for aquatic locomotion. Their legs are designed for running on solid surfaces, not paddling through water. Their body shape, while streamlined-looking, does not function hydrodynamically.

When silverfish fall into water, they flounder on the surface. They may thrash their legs and body in an attempt to reach a solid surface, but they cannot control their movement in water or propel themselves in a chosen direction.

Can Silverfish Survive in Water?

Silverfish can survive brief submersion — they do not die instantly upon contact with water. Their body scales provide some degree of water repellency, and like many insects, they can trap air against their body surface, which helps them survive short periods underwater.

However, prolonged submersion (more than several minutes to a few hours, depending on conditions) is fatal. Silverfish will eventually become waterlogged, exhaust themselves struggling, and drown.

This is why silverfish found trapped in bathtubs and sinks are often still alive — they fell in, cannot climb the smooth surfaces to escape, but have not yet drowned in the small amount of residual water.

Why Silverfish Are Found Near Water

Despite being unable to swim, silverfish are strongly associated with water sources and moist environments. This is because of their dependence on humidity, not because they seek out standing water.

Silverfish need moist air — relative humidity above 75 percent — to:

• Absorb water vapor through their exoskeleton
• Maintain proper hydration
• Support egg development
• Enable normal metabolic function

This humidity dependence draws them to:

• Bathrooms with shower steam and dripping faucets
• Kitchens with cooking steam and wet dishes
• Basements with foundation moisture and condensation
• Laundry rooms with dryer moisture
• Areas around leaking pipes

They are not seeking the water itself — they are seeking the humid air that water sources create.

Silverfish in Drains: Myth vs. Reality

A common misconception is that silverfish live in or emerge from drains. While silverfish are often found near bathroom and kitchen drains, they do not live inside the drain pipes. Instead:

• They are attracted to the moisture and humidity around drain openings.
• They may shelter behind the drain plate or in gaps around the drain fixture.
• They sometimes fall into sinks and tubs from the surrounding surfaces.
• The moist environment around drains is simply part of the humid areas they inhabit.

If you are seeing silverfish near drains, the solution is not to treat the drain but to address the overall humidity in the room and seal gaps around the drain fixture.

Using Water in Silverfish Control

While silverfish cannot swim, water plays a role in control strategies:

Water as a Limitation for DE

Diatomaceous earth loses its effectiveness when wet. Apply DE only in dry areas, and remove and reapply if it gets wet.

Humidity Reduction

Since silverfish depend on moisture in the air rather than liquid water, reducing humidity with a dehumidifier is more effective than eliminating standing water alone. However, fixing leaks and removing standing water helps reduce local humidity.

Jar Traps

The inability of silverfish to swim (or escape wet, smooth surfaces) makes simple jar traps effective. A glass jar with smooth interior walls traps silverfish that fall in, whether the jar is dry or contains a small amount of water.

The Bottom Line

Silverfish cannot swim, do not live in water, and do not emerge from drains. They are moisture-dependent terrestrial insects drawn to the humid environments that water sources create. Controlling moisture and humidity — not water itself — is the key to silverfish management.

For a comprehensive control plan, see our guide on how to get rid of silverfish. For complete information, visit the complete guide to silverfish.

Expert Insight

"Silverfish are not aquatic, but they are remarkably resilient around water," says Sarah Mitchell, BCE, drawing on 15 years of IPM experience. "I have found live silverfish in damp bathroom traps and even in standing water under leaking pipes. They do not swim in any meaningful sense, but they can survive brief water exposure, which is why you often find them near drains and fixtures."

How to Identify

Finding silverfish near sinks, tubs, and drains is common, but positive identification confirms the pest before treatment. Silverfish are 1/2 to 3/4 inch long with a tapered teardrop body covered in metallic silver-gray scales, three tail appendages - two cerci and a central filament - and two long antennae. Their lateral, fish-like motion when running is distinctive. Near moisture sources, look for indirect signs: black pepper-like droppings along cabinet edges, irregular scraping on paper labels or cardboard stored nearby, and shed exoskeletons in under-sink cabinet corners. Sticky traps placed inside under-sink cabinets and along nearby baseboards capture nighttime foragers and confirm active populations before treatment begins.

Risk and Severity

Silverfish near water sources in kitchens and bathrooms primarily threaten paper products, cardboard packaging, labels, and cellulose-based materials stored in damp cabinets. Although silverfish are not a food safety hazard or disease vector, their droppings and shed scales accumulate in cabinet interiors and contribute to allergen levels in sensitive households. The more significant concern is that persistent moisture near fixtures - condensation, slow drips, damaged caulk - creates conditions where silverfish populations grow undetected over months. Addressing the moisture source is more consequential than treating the insects directly, since populations will rebound as long as ambient humidity remains elevated.

Prevention

Preventing silverfish near water sources requires reducing the humidity those sources generate. Fix dripping faucets, leaking supply lines, and condensation on cold pipes promptly. Ensure exhaust fans vent kitchen and bathroom steam outside. Apply caulk around drain trim, pipe penetrations, and cabinet kick-plates to block the damp gaps silverfish use for harborage. Store paper products, cardboard, and anything with starch-based adhesives away from under-sink areas. Run a dehumidifier in bathrooms and kitchens where condensation is persistent. Sticky traps placed inside under-sink cabinets provide early detection and help measure whether moisture corrections are reducing activity over successive weeks.

Main Causes

Silverfish thrive where humidity stays above sixty percent and starchy or cellulose-based food is available. Damp basements, bathrooms, attics with poor ventilation, crawl spaces, and storage areas behind exterior walls are the most common nesting zones. They feed on book bindings, wallpaper paste, cardboard, dried pasta and cereals, dead skin and hair in dust, fabric starch, and any organic material with carbohydrates. They enter through utility penetrations, foundation cracks, and gaps around windows, and stowaway in cardboard moving boxes, used books, and stored documents brought into the home. Slow leaks, condensation on cold-water pipes, and inadequate exhaust ventilation in bathrooms create the persistent humidity that lets a small population establish into a sustained presence.

Solutions and Actions

Silverfish respond to a combined moisture-control and targeted-treatment program. Address the underlying humidity problem first by running a dehumidifier in basements and storage areas to keep relative humidity below fifty percent, repairing slow leaks, improving bathroom ventilation, and resolving condensation on cold-water pipes. Apply diatomaceous earth or boric acid dust in cracks and crevices, behind baseboards, under bath fixtures, and around utility penetrations — these slow-acting desiccants work as silverfish move through treated areas. Place sticky monitor traps in active rooms to verify the population is declining. Inspect cardboard storage, dispose of damaged boxes, and switch to plastic storage bins for paper goods, books, and clothing. Treatment without humidity control consistently fails.

Frequently Asked Questions

Can silverfish survive in water?

Silverfish can survive brief submersion in water but they are not aquatic insects. They may float or crawl along the surface tension for a short time. Prolonged submersion will drown them. Finding silverfish near water sources is due to their moisture preference, not swimming ability.

Do silverfish come up through drains?

No. Silverfish do not live in drains or plumbing and do not enter homes through drain pipes. They are often found near drains because those areas tend to be humid. The silverfish arrived via cracks in walls, gaps around pipes, or other dry entry points.

Why do I keep finding silverfish in my sink or tub?

Silverfish fall into sinks and tubs while foraging along the edges at night. The smooth porcelain or fiberglass surfaces prevent them from climbing out. Finding trapped silverfish in fixtures is a sign of an active population in the surrounding area.

What should I inspect after finding silverfish near water?

Check the humidity source around the fixture: leaking supply lines, loose drain trim, damp cabinets, condensation, and gaps where pipes enter walls. Silverfish need moist air, not open water, so drying the room and sealing pipe openings matter more than treating the sink or tub.

Sources and Further Reading

• NC State Extension — Silverfish and Firebrats
• Penn State Extension — Silverfish Fact Sheet
• University of Minnesota Extension — Silverfish
• NPMA — Silverfish Overview