Well here we got some doug out inland small lakes, mostly 20 - 30m deep, dark, murky green brown sweet water. Then there is the the Northsea which is a sand bottom, shallow with most of the time little visibility and lot's of current. And finally we've got Zeeland (The Original ! - LOL )where the the sea inlets are all but one dammed off. Another arm has got this very expansive movable dam to counter extreme NW storms to prevent national disasters such as happened in 1953 flood. Those arms are pretty nice to dive in, but as guess the visibility is generally poor, the water green, and on average hovering between 12 - 18 c. Not deep either, about 30m at the deeper parts. There are some deeper parts, but those are extremely dangerous with over hanging sand and swift currents far from the shore.
In terms of animals, we've got lobsters, eels, brass, various kinds of flat fish, catfish, sepia, harder, mussels, oysters, sea stars, kelp, anemones, jellyfish (harmless ones)
Here's a video of a typical scuba dive near a well known spot called the Zeeland brug (Zeeland bridge). The visibility in this video approaches the average of 3 - 5 m.
