I started shooting film with a Vivitar manual 35mm in 76. Graduated to a Minolta with 1st generation auto electronics, when I lived in AK in 78. Switched to Nikons in the 80's and still have a lot of Nikon glass.
Started shooting underwater with a Nikonos V Underwater camera in the 90's. I would shoot 20 - 30 rolls of film on a week-long dive trip, get home, drop it all off for processing ($$$), and end up with a dozen keepers, if I was lucky. Later some of the live-aboard dive boats offered E-6 slide processing on the boat ($10 a roll), so you could at least check your exposure within a day or so, instead of waiting until you flew home. In 2002 i decided to take a giant leap and I got a Fuji S2 Pro DSLR. It was based on a Nikon N90 body and it had the Nikon mount so all my lenses would work and my strobes would sync with TTL metering. I housed it in an Aquatica aluminum housing (still have and use). The 1st dive trip with it was on the Belize Aggressor at Lighthouse Reef Atoll (Great Blue Hole) I was blown away after the 1st dive. The histogram instantly gave me exposure information and the playback underwater was the game changer. The learning curve was shortened exponentially. I was the only DSLR on the boat for the 1st few trips but that quickly changed.
I needed something to take down the Grand Canyon in 2008. I wanted something with DSLR attributes, but in a small package. I ended up with a Canon G9 and it has proven to be amazing and bullet-proof. I have had it on 5 different week long rafting trips and over 500 river miles. I have also taken it underwater to 130 feet, in it's proprietary housing, made by Canon. In fact, I'm finding it more difficult to want to travel with the DSLR setup (1 large Pelican roller case and 1 carry-on size case). The DSLR stayed home last spring on my BVI dive trip and the G9 logged another 22 dives. I have also used it to take photos of my honey bees when I go in the hives. It tends to get honey on it from handling the combs and sometimes the buttons get a little sticky. Don't get me wrong, it can't compete with a top end DSLR and high quality lenses, but it is an acceptable alternative that will take a lot of punishment. Last I heard, they were up to the G12 or maybe higher. One of my dive buddies has a G2 that he bought new and it is still going strong.