I have read several articles on replacing an under water light but none said anything about having to lower water level to do this. Please respond.

You shouldn't have to drain the pool to replace the light. Just remove the trim ring, and remove the bulb, or bulb bucket. There is another bucket that stays in the wall. That one is sealed. The conduit should go up to a junction block above ground level fairly near the light. The conduit will be sealed to the light bucket, but the conduit will have water in it up to the water line in the pool. That is why they usually put a junction box near the pool, a few inches above the ground.

Sometimes the wire will go all the way back to the transformer, or breaker panel which is probably near your pump and filter. Maker sure you kill the power before messing with any of it.

Disconnect the wire in the junction box by unscrewing the wire nuts. Or take it loose at the supply panel if you don't have a junction box. Use some black tape and tape a string to the wire going down to the pool, so that you can use that for a "pull wire" to pull the new light wire in.

After the wires are loose, then you can pull the bulb and the wire though the conduit. Pull it until your string is above the water line. Then untape the string from the old bulb and wiring.

Then, stretch out the cord, and cut the cord on the new bulb to match the length of the old one.

Now, tape the string to the new cord.

Pull the wire and string through, then place the bulb in the bucket.

Replace the wire nuts on the wires.

Place a ball of duct seal (ask at your building or hardware supply) around the wire to seal the conduit coming in from the pool. That will prevent corrosion from occurring in your junction box.

That fits the majority of them. There are some that are sealed socket type bulbs without the wire attached. You will do most of the above steps to get the light bucket up above the water line if that is the case. I think you can probably figure that out.

If you need anything else, let me know. I'll try to help. If this isn't making sense, get me pictures, or model #'s of your light. Then, I'll try and be more specific. But, there's a high probability that the above instructions will do it for you.
Good Luck,
Al