I agree with the general sentiment that supervision, proper floatation devices and experience will quickly lead to lots of fun, regardless of depth. Building strong swimmers who are aware of their own limits is your best defense. If you do pursue some form of barrier between the shallow and deep ends, just make sure that the openings are small enough that arms and legs can't get stuck. In many cases a plain old blue and white bobber line may do the trick, clearly denoting the change from shallow to deep and giving a tired or panicked swimmer something easy to grab onto
And at the risk of the old lifeguard in me coming out (10 years of commercial pool management heck starting in the mid-1980s), the home made bench pictured above in DIYLiner's post, while a great idea, does present its own safety hazard, as a person could slip underneath and not be seen from above or - worse - get stuck. Any platforms used in a pool should have a solid base that goes straight to the bottom on all sides so that no one can slip under OR have decking that is constructed so that a body underneath can be readily seen. (The former is definitely more desirable than the latter, IMHO.) Same reason you shouldn't swim if you can't see the main drains: all swimmers should be visible from the deck at all times, even in a home pool Additionally, make sure there are no fasteners sticking out that could snag a bathing suit or cut a finger. Apologies for being overly cautious, but I saw a lot of really poorly designed equipment in my guarding days, and witnessed some injuries resulting from it. Home pools carry many of the risks of commercial pools.