The trouble with trading for something smaller is that you are going to sacrifice manual controls for the most part. And that means that your options, especially underwater, are going to be more limited and you'll need to learn to work within those new limitations and be happy with the limitations.
Or keep your A 620 for underwater and get something like the Canon SD1100 to carry around for land. I was this close yesterday to pulling the trigger on this model as I am very unhappy with my Olympus 720SW. Others are willing to live with the below average picture quality & slow and often inaccurate focusing of this series for the benefits it undoubtedly gives. I've been happy to sacrifice those things for a while now, but it's getting harder and harder to accept, especially when I know there are models out there that don't make me crazy...but those models don't offer the things the Olys do...all of life is a tradeoff! And I'm keeping the Oly as it definitely is a useful tool - it just wouldn't be my only compact camera.
I haven't used the newer Olympus 1030SW very often yet and it does appear to be slightly better (although still a bit slow and misses focus though) than the three models before it, so if ruggedness, a bit of built in waterproofness (watch the seal on the battery compartment!) and 10/10 style factor are important this is the model to try. But it's also heavier than something like some models in the Canon SD range.
In a nutshell for the SD range, thanks to tons of reading and talking to real world users, I "narrowed" it down to: SD700, SD770, SD850, SD870, SD950, SD1100 (I think I remembered those right LOL). For what I was looking for, the SD1100 fit the bill pretty well.
Pentax also do an Optio waterproof camera but I haven't been able to lay hands on it. I have one friend who has it and uses it for everything day to day, but not in the water beyond rain & snow. She loves it and has several 8x10 (one might even be bigger, can't remember) displayed and they look lovely.
There are tons of choices out there and not every camera will be right for every user. Most of the cameras from the major players will do an OK job for most people's needs. If you have needs that are a little more demanding than Auntie Jean, then you might have to look a little more closely.
Have fun shopping!
Shopping is fun 
