Hey there,I'm looking to build some (probably about 4) battery-powered lights to add underwater color light effects in a bathing lake. They will be placed near a floating platform to make swimming there more enjoyable. The water there is approximately 6 meters deep, but I do not know the exact depth yet.My current plan is to put colored LEDs (one color per unit) with one or two 18650 batteries into something waterproof and transparent, that has enough volume to float, and attach it to some kind of weight (a stone for example) with a string. The string would be long enough to make the light stay about one to two meters below surface, enough to make it possible to swim above it without touching it.Here is a quick sketch to explain what I mean: https://ift.tt/2Iuht21 requirements are as follows:at least 3h light duration until power runs outbright enough to be seen from ideally 5m, but at least 3m distance underwaterwaterproof (duh)cost less than €20 per unitI do not have much experience with building such things and therefore have a lot of questions:Which LEDs to use?What kind of container to use? How to make sure it's waterproof? How to make sure it's retrievable after use? How to make sure the batteries are changable without too much effort? How to make sure it doesn't break easily?Which LEDs to use?I did some research but didn't really find what I was looking for. Most LEDs marketed as "high-power" have around 40 to 80 lumens, which doesn't sound like enough to me. example Also, many operate at weird and wildly varying voltages. That would make it hard to just connect it to the batteries.Are there colored LEDs with operating voltages around 7v (two 18650 batteries) with 200 lumens or more? Will that even be enough brightness to be visible from 3 meters underwater? Are there good onlineshops to buy from (from germany)?What kind of container to use?Would a simple plastic box be enough to house the LEDs or will I need something more sophisticated? One 18650 battery weighs about 60g. That should mean that the entire light-unit would probably weigh under 200g, which means it will only need around 200cm3 of volume to provide buoyancy.Are these calculations realistic or did I miss something?I would really love to hear your thoughts and ideas about this project. Any help is very appreciated. via /r/DIY https://ift.tt/2KfjTyE
