Article by Capt. Steve Katz
Underwater Lights
A walk down the docks at nightfall will reveal many boats with colorful lights illuminating the water around the boat. Underwater lighting is certainly not new but has advanced in recent years. Let’s look at some of the modern advances in underwater lighting.
Underwater lights are special lighting fixtures that are attached to or installed into the hull of a boat below the water line. Most underwater lights are installed on the transom or hull sides, only a few models and brands of lights are designed to be installed on running surfaces.
While lights that attach to the hull are the most popular, there are a few underwater lights available that can attach to other underwater items, like trim tabs or even replacing the transom drain plug. Most underwater lights require drilling a hole into the boat, below the waterline to route the wire from the light to the power source. There are a few surface mount underwater lights where the wire is surface mounted to the transom and runs through openings above the water line.
The most popular underwater light is a surface mount fixture that requires a small hole, usually less than ½” for the wire to enter the hull. This style light is mounted on the surface of the hull and usually protrudes about ¾” or more from the hull surface. The light fixtures are attached to the hull with screws and sealed with marine underwater sealant.
The top-of-the-line type of underwater light fixtures is the thru-hull style, where a fixture is installed through the hull, often in a hole of 2’ or larger in diameter, that is accessible from inside the boat. These lights are two parts, the light source and the thru-hull fixture. The major advantage of this type of underwater light is that the light can be serviced, repaired, replaced or upgraded without hauling the boat out of the water. This type of light fixture is virtually flush with the hull surface providing a cleaner look and less likely to interfere with fishing activities etc.
Underwater lights are available in many colors and intensities. While most current product offerings use a LED light source, many of the original underwater lights used an incandescent light source such as halogen, tungsten or HID type light sources. Even with today’s LED offerings there is a wide variety of brightness and colors– generally proportional with cost.
The most basic underwater lights are offered in a single color, often white or blue. Higher end options include multiple colors or even an unlimited color pallet. Controlling these light color options can be as simple as the flip of a switch or as complex as using your boat’s MDF/ Chartplotters to graphically control the lighting. For even more options, underwater lighting (and deck lighting) can be synchronized with a source of music on the boat – yes, think disco!
Electrical requirements vary depending on the brand and model of light. Most modern underwater lights are operated with a 12v or 24v DC power source. While many boaters think a LED, it does not need much power and unintentionally undersized the power wiring, causing problems with the light’s operation. Manufacturers, in an effort to offer brighter and brighter lights, pack more and brighter LED’s into the fixture, requiring more power than intuitively expected. One brand of underwater light, Lumitec, has a built-in protection circuit that will automatically dim the light if the power supply is inadequate, often resulting in curious “blinking” lights.
Underwater lights are available in a wide price range, beginning around $100/light and going up to $2000/light with a few as much as $5000/light. Surface mount lights are the least expensive and the thru-hull lights are often 2-3 times as much as the surface mount lights, along with a more complex installation procedure.
Installing underwater lights is often best left to a professional though skilled do it yourself boat owners can install lights by following the manufacturer’s instructions. Here are a few tips:
Access- Installation requires knowledge of the outside and inside of the boat’s hull, you need to be sure the outsi
de area where you plan to install the light does not interfere with the operation of the boat or accessories. At the same time, the inside of the boat needs to be accessible behind the light to gain access to wiring or the fixture depending on the style. The mounting surface must be flat so that the light fixture can be attached properly and create a waterproof seal to the hull.
Location
Most underwater light manufacturers recommend that the lights be installed 6”-12” below the water line. This is important since most light fixtures are cooled by the water, if mounted too high or even above the water light may cause the light fixture to overheat and may be permanently damaged. Most Lumitec brand lights have a thermal sensor, reducing the light output to prevent overheating.
Sealing-Once the location is determined, as part of your preparation, be sure to remove the bottom paint under the light mounting surface so that the underwater sealant can properly attach and seal the light fixture to the hull. Most manufacturers provide details on the type of marine sealant to use and where to apply it to ensure a watertight installation.
Wiring
Be sure to check the manufacturer’s requirements for power requirements and wire size. Do not judge the wire size by what the manufacturer uses at the fixture, usually this is a short run that is expected to be attached to a heavier wire to make the long run to a switch or power source. Many LED’s are susceptible to problems with low voltage which are a result of long runs of undersized wire. While connecting the lights to each other at the transom seems like a good idea, it’s often better to run each power wire to the light switch or source of power – this eliminates a junction in the bilge area and often ensures proper power to each light.
Caution
The USCG often reminds us that “Boaters should be concerned about installing “decorative” lighting on their boats in various places, including underwater, on the rubrail, or just above the waterline. Care must be taken that these lights: cannot be mistaken for navigation lights, do not impair the visibility or distinctive character of approved and properly placed navigation lights, and do not interfere with the operator’s ability to maintain a proper lookout. Such circumstances may represent a violation of Rule 20”
Specific to underwater lights, the USCG cautions that “blue underwater LED lights can appear to be flashing if there is any wave action, giving the appearance of a flashing blue light only authorized to be used by law enforcement vessels per 33 CFR 88.05” Some states even outlaw the use of any type of blue light when the vessel is underway. Most of these regulations do not apply while the vessel is tied up at the dock.
Attracting Fish
Most boaters with underwater lights can attest that the lights attract fish at the dock and while night fishing. Underwater lights may not attract the species you are targeting but may attract smaller fish in the food chain of the target species. Scientific research shows that most fish have eyes that are sensitive blue and green- so if your goal is to attract fish, be sure that your lights can produce either or both colors.
Adding underwater lights or upgrading underwater lights is a popular project for many boaters. There are many manufacturers offering a myriad of products suitable for most any boat and budget.
Until next time, stay grounded! §
