First, I'm taking this to be about fighter jet aircraft and similar. Airliners, general aviation jet aircraft, and others, are different, and there have been plenty of examples of jet aircraft ditching in water and everyone surviving. US Airways flight 1549 is a relatively recent (January 2009) example where an Airbus A320 jet aircraft landed on water. It's not something you want to do, and it's not something that happens regularly, but given the right conditions it absolutely can be survivable.
Modern fighters are unstable. They won't maintain stable, even descending, flight on their own; rather, they require constant, tiny adjustments to their control surfaces just to maintain level flight, let alone maneuver. This is done because it allows much tighter maneuvering, which is a much-sought quality in many small military aircraft. As long as everything is working correctly the computers handle much of the minutiae of this, so that the pilot can focus on their mission.
If the pilot is going to eject, you want to do that at some altitude, if for no other reason then because the parachute needs time to deploy. You don't want to eject near the ground if you can avoid it, and not all planes that have ejection capability are rated for zero-altitude ejections. Few are rated for "zero/zero" (zero altitude, zero forward speed) ejections, which are basically "sit on the tarmac and pull the lever".
Every aircraft (actually, airfoil) has what is known as its stall speed. This, simplified, is the lowest speed at which controlled forward flight is possible. The exact value for the stall speed varies both with the aircraft and with conditions (temperature, load, control surface settings, ...) but any fixed-wing aircraft needs considerable forward speed for the wings to generate sufficient lift to not stall. Landing an airplane is, very broadly speaking, executing a well-controlled stall. Once the aircraft gets below its stall speed, it becomes basically a large brick, and drops towards the ground. (Things like vectorable thrust and VTOL designs make this somewhat more complicated in reality, but the basic principles are similar.)
It is correct that by pitching up, you are going to lose forward speed (due to drag). The axiom when landing a fixed-wing aircraft goes like power for altitude, pitch for speed, meaning that you adjust your altitude primarily by adjusting power, and your speed primarily by adjusting pitch (nose up or down). (Compare this to movies, where the direction an aircraft is moving in is often controlled almost exclusively by the control column or stick, and seemingly almost never with power.)
Now, let's apply all of this to your third bullet point:
- When you're as low as possible (but still high enough to allow this maneuver), suddenly pull up the nose as high as you can while keeping altitude constant as long as possible
I expect that, if done properly, this could nearly halt horizontal motion of the aircraft; when the momentum is finally lost, I expect the plane would suddenly "drop" in the water from a few feet above [...]
Yes, it's probably going to slow down the aircraft's forward speed.
Unfortunately, the aircraft will drop when it slows down below its stall speed, at which time it still has a significant forward speed.
This means that when the aircraft hits the water, it is still moving forward quite fast. Fast enough that the water doesn't have time to move out of the way.
What you are doing then is akin to performing the same maneuver over a similarly rough concrete surface. Remember that by the time you are even considering ditching in the first place, the aircraft is probably damaged or crippled in some pretty fundamental way; otherwise, why not just land normally? Even a very hard landing that ends up breaking the landing gear is far better than a ditching. Unless the water is near perfectly smooth (similar to a runway), when the aircraft hits the water, it is going to come to an abrupt halt, which causes significant forces both on the airframe and its occupants. It's like they say, it's not the fall that kills you, it's the sudden acceleration at the end of the fall. (Conditions may apply.)
[...] it certainly seems to potentially beat jumping out of your plane at 15,000 feet and risk getting chopped up by the tail or having your parachute not open [...]
"Risk getting chopped up by the tail" is why any sane ejection system starts by giving you a significant vertical boost. "Having your parachute not open" is a risk, but that's why parachutes are inspected regularly (they are not set-and-forget items by a long shot!) and it probably still beats crashing in an uncontrollable aircraft.