IMHO, the key spec on a macro lens is 1:1 magnification. They are primes too (no zoom). For full frame cameras, Canon makes 65mm, 100mm and 180mm models. The longer the lens, the farther the working distance. With my 100mm, I can get the tip of the lens about 6" away from my subject. With the 180, I believe it's about 3 feet between subject and lens, which can be handy for skittish subjects like insects. The 65mm is a special beast with variable magnification.
Taking macro pics is just like taking any photo in terms of basics like exposure and composition. Understand those, especially the holy trinity of exposure (aperture, shutter speed and ISO), and you're most of the way there.
Reef photography is a bit of a specialty, as there is often high color temperature lighting involved, such as the light from my 20,000K metal halides. To make the colors in the final image look like what my eye sees, instead of very blue, I shoot in RAW mode and adjust the white balance of the image during post processing. Lightroom is my friend.
When not shooting in RAW, the file that gets saved is a jpg which has already had in camera white balancing and compression performed. Because of the niche aspect of high color temperature lighting photography (reef), cameras aren't designed to properly white balance images shot under high color temperatures. Shooting in RAW, the file that gets saved is not a jpg but contains the unprocessed, uncompressed (raw) image sensor data. Then the photographer can make the decisions about appropriate white balance and file size. Plus Lightroom is nondestructive, so the original file data is never altered, unlike a jpg which typically looses image quality with every save and re-edit because of compression.
I find I take more time doing macros, but that's because of the way I shoot. I shoot tethered to my laptop and control all camera functions except focus through my computer. I can trigger autofocus with the computer, but I am usually shooting all manual, so I don't do that much.
Shooting remotely / tethered allows me to use my 15" laptop screen instead of the back of the camera, which I find invaluable. I can analyze the shot way more carefully and make sure the focal plane is exactly where I want it.
I find a tripod is a requirement. I often go with longer shutterspeeds and would never be able to get a sharp pic handholding for that time. A remote shutter release is very handy, so one is not blurring the image by jiggling the camera pressing the shutter release on the camera body. If one is not available, at least use a timer so the button press and exposure capture don't occur at the same time.
This may seem like a lot, but take a step at a time and you'll be a master eventually. You can always get feedback from people here. The photo you're struggling with may be the best learning tool for yourself and others.