I completely agree with Tim!
Adobe's Creative Cloud for Photographers plan offers both Lightroom and Photoshop at an attractive monthly rate. I would suggest that this is the best way forward for photographers now. You just have to get your head around "renting" software as opposed to owning it.
If you are looking for an app for photography, Lightroom is pretty much the way to go. If offers a more intuitive and streamlined workflow for image ingesting, processing, editing and exporting. Photoshop is an amazing graphics package that does an amazing number of things very well, but as a photographer, it has a huge number of functions atet you will need use.
The Elements packages are limiting, as their emphasis on "templates" doe not really suit underwater imaging.
There are a bunch of online resources for Lightroom and a number of excellent tutorial/seminar options for learning about it.