Those are awesome nice pictures. I just can't take them under my Canon dslr, lol. I need to take a photography class.
Sounds like you got the camera, just get a viewer for top shots and play around with it.
Here's my base setting that works for t5
Set your Kelvin as high as possible (higher the number the better for blue shots. Mine let's me go up to 9900k. This tells the camera a blueish white is actual white and helps correct the photo and reduce blue.)
Set you exposure (usual a "+/-" symbol) low, in the negatives. Midday t5 shots mine is usually at -0.7.
Turn off auto select focus - where the camera choses what to focus. This keeps the focus centered in the view finder making it easier to lock in on the subject.
Turn flow off a few minutes before shooting, gets debris out of the shot
Download canons editing software. It'll be free on their site. There will be a graph under editing that has RBG ( Red, blue, green) in the drop down menu. Select B for blue. Click the line and pull it down in the middle slightly to reduce blue. I do this until the picture doesn't look super blue but reds and greens don't look over powering. A trick is to ask yourself if the water looks super cold to the touch, if it does you're still too blue.
Contrast increase to 5 out of 100 gives some shadows a d depth. Helps draw attention to the coral....and away from my bubble algae.
Sometimes bump up the sharpness on macro shots.
That was meant to be shorter but it took me awhile to figure those settings out, so maybe it'll save someone frustrations. I shoot on a nikon but I'm sure everything is similar for a Canon.