yeah, just don't leave it submerged for too long or it can drown (highly oxygenated water may prevent that? )
you can google for suggestions on this methid... they range from 1/4" to 2" on the root before you plant it... if you leave the shell above ground, you'll have to gently remove it later -- but do have some patience... that's why this method is bad.. it promotes stupidity through OCD behaviour lol... if you can stay away from the silly stuff, it's as good as any method. The risk with this one is contaminating the root as well as exposing it to light. you'll just confuse the diversification of cells that is occuring.
i'd suggest planting immediately. use some clean to pick it up and place it gently... the root can be buried straight down, but if you don't want to pick off teh shell, bury that portion 1/4" or soand a little bend / horizontal at tip. This will force it to do what it normally does... grow out and wedge itself upward, which will pull off the seed shell for you without picking at it or potentially damaging a sensitive seedling.
people like starter cubes and such, but if they absorb water differently, you'll have odd things happening with wicking water away from the substrate or pushing more into it etc etc... i like to keep it simple. a cup of my coco. 2+ days later it sprouts. no delicate procedures you'll eventually screw up by ripping off a cotyledon or giving the root some sort of disease before it even starts. plus, it matches the end home (or start aeroponics if ebb/flow, dwc, etc)
