I don’t know much specifically about Lake Sirena, but it is plenty big enough to ski on.
The following website will tell you a little more about Highlands County lakes.
http://www.highlandsswcd.org/everything/lake_summaries/Highlands%20County%20Lakes.htm Since it is a ridge/sandy bottom lake it should be fairly clean and have good water clarity. Just as an example of size, I live on a private lake in Avon Park (Lake Isis – approx 25mi north) and it is approximately 65 acres. It is more like a typical ski lake where you make a pass and then turn around go the opposite direction. This works fine unless there are other boats or jet skis on the water and then there is too much chop. Lake Sirena is probably close to 3x as big as our lake with 3x the number of homes.
Probably the best lakes in Highlands County would be June, Jackson, Lake Placid, Lotela, Grassy or Huntley. There are also a number of smaller private or semi-private lakes to choose from. The most expensive would be June & Jackson although you can usually find a big price range on each lake depending on the area of the lake. The housing market is still very slow so probably lots of deals to be had.
By the way, there are probably several of the animals in your profile pic in Lake Sirena (and most other lakes in the area).