I agree, the mosquito is not hard to use. O would suggest "playing" with it until you are certain of how it will respond. A pool session is good for this, because you have to get below 4 feet before it completely goes into "dive" mode. You can sit on the bottom and safely try to confuse it, resurface, practice checking the log (notise the difference between how it lists DAY of dive(s) and then the individual dive(s) of that day) and then go down again and try the different modes.
As far as I know, there's no way to purposefully or accidentally force the important information off the screen while diving. For instance, I don't think you could get into log mode while it knows you're underwater. The two bottom buttons, left and right, will cause the two small bottom numerical displays to switch between two displays each. I'm not looking at it right now, but it's SOMETHING along the lines of... the left button switches between bottom temperature -or- elapsed dive time, and the right button switches between current time and something else, but DON"T take my word for it. However, it's pretty obvious when you try it out.