Panda

For a one off trip it's probably not worth it. You really need an external flash as well and a macro lens for a functional underwater setup. 

Best to concentrate on enjoying the diving and don't let the camera take over. Don't expect photos of a lifetime on your first attempt and without the appropriate gear.

You might find video will give you better results first off

No problem divengolfenfish,

Anyway I think I learned all I know from Aussiebyron

Same here, AF-S, although I leave it on multi point through laziness. You need to think in terms of single clips of a specific subject, rather than making up your mind as you're recording.

Choose the subject, focus then record the clip. Refocus for the next clip, record, etc. You can refocus during a clip but you would want to edit out the refocussing section.

A page of my settings here.

My rule of thumb is...

As good as brand new, Mint condition, for latest model camera - 3/4 new price

Used, for latest model camera - 1/2 new price

Used, superseded camera - someone please buy my housing

Good blog Interceptor. Keep it up.

The GoPro is great for "Guerrilla" timelapse but any lighting changes send the WB haywire