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How to Determine your System's In-Water Weight

Written by: Meg Griffin
Photography by: Tim Sullivan

January 2020

 

In the age of modern underwater photography we are often asked, “how much does my system weigh underwater?” or "Which float arms do I need?"

Unfortunately, these questions don't have straight-forward answers due to different ports, lights, and mounting systems having different buoyancies underwater. Fortunately, we have found a wonderful solution to this dilemma...

weighing your system in-water! 

 

Sounds easy enough right? And it is! All you need is water deep enough to submerge your entire system and a fish/luggage scale. 

Step 1: Locate your “Body of Water”

 

You can use any water for this, it does not need to be saltwater or fresh because the difference in salt densities differ across the seven seas anyways, so we’re just looking for a ballpark here. If you are lucky enough to live near a body of water that you feel comfortable submerging your underwater system in then you can simply use that, and if not then you can create your own. We here at Reef end up using a large garbage can that we dedicate to weighing our customer's systems, it works great as it is deep enough to fully submerge the system but also narrow enough to not use too much water. 


Step 2: Assemble your system-minus your (future) float arms

Because each item has a different weight in the water, it is best to assemble your system fully minus the arms that you plan to replace with float arms. This will give you the most accurate weight of your system. If you are simply looking to determine your system's in water weight without any plans to purchase float arms then you can weigh your system fully assembled. It is also important to remember that if you dive with different ports or configurations it is necessary to weigh your system with each port intact. So if you sometimes dive with a macro port and an external wet lens and sometimes dive without a wet lens, then you should weigh your system each way- the same goes for domes and other accessories. It is also worth mentioning that we at Reef will always clean the housing o-rings and set a vacuum before this step to ensure that we are avoiding any accidental flooding, even with something as simple as placing the housing into a shallow tub of fresh water. 

Step 3: Hook the scale onto the housing

Make sure you have the ability to keep the scale above water while keeping the rest of the housing, arms, clamps, and lights underwater. We will usually attach it to a clamp, arm, or part of a tray.  You can also tie a piece of fishing line from the housing to the scale if you need more space.  

Step 4: Completely Submerge the System

In submerging the system it is important to make sure that everything is underwater and not touching the sides or bottom of the tub. Hold the luggage scale right above the water, only allowing the hook to get wet and no other parts of the scale if it is not waterproof. 


Step 5: Read your Weight and Choose your Float Arms 

We carry a large variety of float arms here at Reef Photo and Video. We have float arms from Nauticam, Inon, and ULCS, as well as the adjustable closed foam Stix floats for smaller adjustments. Each product listing shows the amount of float the arms provide and if you are planning on using two or more arms then remember to account for that in your calculations. Most divers prefer having their system a little negative so if you do not have a preference then that is a great starting point. If you are using multiple port configurations you can purchase a set of normal float arms and make small adjustments using the Stix Jumbo Floats. 

You can view all of the float arms we carry here