You're lucky whoever your matching against hasn't started using Dtilt; for Ike it's a dunk over the edge.
I've been grappling with this match up for months (being my friends main is Ike)
He converts wins on most games but I found there are a few mix ups and must do's to keep above the water.
His neutral combo is excellent but not perfect. It has enough frame lag between attack 1 and 2 to grab out of shield. It is one of his fastest ways to put you in a tumble though. Utility wise the move is crazy. Recognize this move and if you can bait the combo out it has (as most Ike moves do) massive back end lag.
His dash will out trade yours alot being he can deploy it earlier then you think and still connect. Its not easily "hopped" over and a back and forth dash dance will work but can sometimes still get you hit. A down dodge should put you in good standing because of the lag off the back of his dash, but if you must get hit you HAVE GOT TO tech it. If you can't tech his options are usually to great and soon you're off the ledge where again his options are superior in most every way.
As for recovery mix ups are the only choice to get you back more times then not. I spend 70% of the time in these matches (even those i win) on the left or right of the stage sideB'ing for my life. If you are above him you can't faint a fast fall and then draw an attack with a side B. If you can't make it that far you can drop counter (don't always advise this).
The real trick to your mix up is save your jump no matter what (odd circumstances need not apply) try to draw out the charged attack or convince him that you're not gonna make it.
Then wait for his overcompensation to your recovery adjustment. If he's to close to ledge give him an early up B...etc
As for the mid game with Ike getting him above you is your best chance to survival. Once you can pop him up be fresh with your tilts and up airs. "At least in my case" Ike can't deal with an air game from below. BEING ABOVE HIM IS NOT ADVISED. For this reason I actually don't use as many short hop approaches and instead rely on spacing/Ddancing/and Down dodges to make grabs and convert them in to air combo's.
As for taking that stock...
You can't easily kill him when he's OP's for an Aether (upB) recovery due to the zoning of the sword he throws. (note: If you get cheeky you can get over the sword and dunk.). You can't even easily edge hog this because one missed frame Aether will put you under the stage. You have to use patients and spacing with Aether and punish any Ike that would land on stage rather then grab ledge.
As for his Side B recovery, "quick draw".
If you recognize this recovery you can easily leave the stage to punish it. But a very basic level this is a slow version of space animals side recovery and should be easily punished with a side B or even a Ftilt or Dtilt. They may OPT to go high with this recovery but Bair and Fair are built to deal w/ this threat.
In short space/block/dodge Ike's slow moves like Fsmash, Dash, etc... And, recognize when a neutral combo is imminent and act appropriately. I know I'm wordy but I hope this helped. Message me if you have a specific question
