Simplex sounds good but would the Apex be better if I intend to do some gold prospecting in the creek. Creek is about 12" deep or less
Hopefully Monte will weigh in on that. He has a lot more experience (with the Apex and detecting) than I.
Nugget hunting isn't an option where I'm at (southern NJ) but the Apex has the option of higher frequencies (in single frequency) and the simultaneous frequency mode (MF) uses a higher frequency as well. Therefore - presumably - the Apex should be better on small gold.
I wish I could give a more precise answer, but I've never hunted for gold nuggets and cannot say for sure one way or the other.
The Apex will be perfectly fine hunting in 12 inches of water. Just don't let the control box get dunked.
Swing slow (with whichever machine) and overlap your swings. It helps to "test" your machine by putting multiple likely-to-be-found targets on the ground and swinging over them. Note the tonal response and the VDI (number on the screen) for each target. That will give you a rough idea of how your machine responds. It is likely that your machine (whichever machine chosen) will respond a bit different to targets actually in the ground - and nearby trash will alter the response to one degree or another.
Since it is your land - I'd suggest that you dig everything until you learn what the machine is telling you. Trash (iron) can make the VDI read lower than the good target (in the same hole) but higher than the trash (in the same hole).
I mostly hunt areas that have a lot of iron trash - small bits of square nails, farm machinery, etc.. If I get a good tone, even if it is only 1 way, and the target isn't large - I dig. A lot of my good finds are found with trash in the same hole.
Garrett has a number of videos (regarding the Apex) on their website. Watching them can give you an idea of how the Apex works.
There are also a lot of videos on the Simplex (Youtube). They can be a good way to learn how that machine works.
For the record: I do not own a Simplex (no reason to, since I own other NM machines that have additional options and abilities). I have used a Simplex for a short time (helped my neighbor learn his). It is a very capable machine.