Fluid goggles are a specialized type of eyewear designed for underwater use that are literally filled with water. This unique design fundamentally changes how they interact with pressure at depth, offering a different experience compared to traditional air-filled masks.
The Core Principle: Water-Filled Design
At their heart, fluid goggles are exactly that, filled with water. Unlike conventional diving masks that trap an air pocket in front of your eyes, fluid goggles remove this air space by replacing it with water. This eliminates the need for divers to equalize pressure within the mask by exhaling through their nose, a common technique used with air-filled masks to prevent mask squeeze.
Pressure Equalization with a Collapsing Membrane
To manage the internal volume and prevent discomfort or injury, fluid goggles often incorporate an ingenious mechanism involving a flexible membrane.
- Flexible Membrane: These goggles commonly feature a membrane around the lens that collapses. This flexible material is designed to flex inward as ambient water pressure increases with depth.
- Preventing "Eye Suck": As the membrane collapses, the air space gets smaller, or more accurately, the water inside the goggle can shift, and the flexible lens itself can deform inwards. This mechanism ensures that the pressure inside the goggle remains equalized with the external water pressure. By doing so, it doesn't suck your eyes out, preventing the uncomfortable and potentially harmful effect of "mask squeeze" on the eyeballs, which can occur with rigid air-filled masks at depth if not properly equalized.
Practical Considerations at Depth
While highly effective, the design of fluid goggles does come with a particular sensation that users need to adapt to:
- Membrane Contact: At depth though the membrane will touch your cheek, as it collapses inward to equalize pressure. This physical contact can be an unusual feeling, especially for those accustomed to traditional masks.
- Getting Used To: This sensation takes some getting used to especially if you're in cold water. The cold water conductive through the membrane can make the sensation more pronounced.
Summary of Fluid Goggle Mechanism
| Feature | Description | Benefit / Impact |
|---|---|---|
| Water-Filled | Goggles are completely filled with water, eliminating the air pocket in front of the eyes. | No need for manual mask equalization; reduces mask squeeze on the face. |
| Collapsing Membrane | A flexible membrane around the lens can flex inward. (Hektometers have a membrane around the lense that collapses.) | Allows the internal volume to adjust to external pressure changes. |
| Pressure Equalization | As the membrane collapses, the air space gets smaller, matching the external water pressure. | Prevents a vacuum effect and ensures the goggle doesn't suck your eyes out at depth. |
| Physical Contact | At depth, the collapsing membrane will make contact with the wearer's cheek. | Requires adaptation from the user; sensation more noticeable in cold water. |
In essence, fluid goggles offer a unique solution for underwater vision by replacing air with water and using a flexible membrane to automatically equalize pressure, thereby preventing the common issues associated with air-filled masks at increasing depths.
