Water is much more than H2O. It is alive - from the small diatoms up to the majestic whales. That's why I'm diving since many years.
Diving in lakes has pros and cons. Pro is that you do not have to bother with salt corrosion, heavy current, dangerous creatures and so on / con is that it is often f...ing cold (even in hot summers below 10 meters), visibility is far less than in saltwater (except some groundwater lakes or springs) - Thus you need a warm suit and mentally a certain coolness. But I do most of my dives in the nearby lakes and might not miss them.
In Switzerland we have some rivers with overwhelming dive spots. Most of them are in the south - Ticino. But there are also kind places in the Rhine and other rivers. Visibility can hit the Maldive class sometimes. The environment with rocks and blocks is often ravishing and you can discover a lot of fish like trouts, eels or catfishes.
Sure! this is what I like most ... the longest dives, the variety of creatures and plants, good to excellent visibilities, wrecks, shark schools etc. etc.
But at the bottom - every habitat in the water is worth to visit, to enjoy ... and to leave it untouched!