"Boats Boats Boats!" is literally the name of one of my lists. I don't expect many people to get the ref (HIMYM isn't as popular here in the UK).
A Raider in another Raider would be a thing to see.It is, the one thing that Drukhari do well. Raiders in boats, Wyches in boats, x9 Heavy Boats...Just not Wracks in Boats.
For a while Scourge and Hellions could get in them as well, but the errata put paid to that particular shenanigan. And I've heard debates about putting Mandrakes in them. I've also seen a list that is literally just two Spearheads with 9 Ravagers and 3 Tantalus (Forgeworld Ravager variant). Ob-Sec is for people who don't aim for tabling everytime.
Don't get me wrong, there are plenty of non-boat Dark Eldar units that are fine/fun. The boats are just the ones that no-one else does. (Harlequins do a decent job, but they don't have as good stuff to fire out from inside. Don't mention Sister's Repressors unless you want Forgeworld to get banned in your group.)