Congrats! I’m close to the Dora Chain of lakes, but have been on the St. John’s a few times. Lake George is a rather shallow lake, especially by the Springs. You’ll be fine, but just to be mindful not the “idle” in neutral when in the shallows (not sure if you’ve seen the video posted here, but the intake/jet wash creates a vortex sucking up sand/sediment).
I have heard that on busy weekends the springs can be closed off for crowd control purposes, so head out early. I can’t say I’ve been, as one one of my ventures, Silver Glen was closed (early days of COVID when the state was “shut down”).
To the south, down the St. John’s, there is Hontoon Island, a state park that is only accessible by waterway, and there is also blue springs (you can’t boat in spring, but you can “beach” the boat and walk the park and see the springs from the boardwalk. Never been North of Lake George, but have heard its a nice cruise up to Palatka.
What I’ve noticed about the St. John’s is that on breezier days (winds 10-15), its still a pretty calm water way, as it meanders through the thick swampy forest, so its shielded from the wind, and the waves typically don’t build. You do still need to be mindful where it intersects with other larger bodies of water, as it can get kicked up (Lake George, Lake Dexter, Lake Monroe if you venture that far south).
Don’t know if you have any “mapping/guidance” software, but it might be helpful until you learn some of the landmarks. Three other things to note 1) The bombing range and associated pillings; 2) The “Cow Pens” on the south side of the lake for safe navigation back into the Saint John, 3) apparently the lake has a rather high SALT content, so be mindful of finishing and flushing your boat. The first link is the NOAA chart, the 2nd is a rather interesting read about the lake and clearly shows the “bombing range”.
https://charts.noaa.gov/PDFs/11495.pdf
Lake George Information Guide - Florida Lakes