I'm assuming as you are reading this, that you are beyond using disposable cameras.
Of course, what you want, can be done
with expensive, 'high-end' digital 4/3's or SLR' cameras in a purpose-built underwater housing.
Do you need the bulk and cost?
The higher end compact camera range is the 'sweet spot' for quality photos to print to canvas
(ie good size), compactness and value for money.
You don't need to go 'expensive' but there are limits below which compact cameras lack essential
features to be able to 'cut the mustard' for underwater shots.
a) underwater specific to camera model
(gives access to all camera controls/ menus)
ie ability to use the zoom
ie control of, and access to, the flash
(sometimes want no, half or full - flash etc.)
b) able to be sorted
RAW - easiest, best if camera offers it - go fo it
'custom white balance' - effective but repetitive
in-built 'white balance = underwater' setting - simpler but slightly less effective
c) a for the (LCD) screen
(essential but can buy separately)
a) shutter priority (rather than programme/ auto)
b) shutter speed = 1/250 (my choice)
c) white balance = 'underwater'
(don't confuse with underwater mode or scene)
d) ISO = 200 (my choice)
e) initially flash set to off
f) initially 'normal' rather than macro or super
g) colour set to 'vivid'
h) sharpness set plus 1
i) contrast set plus 1