If you're floating, it was too high :-)
Essentially, he's right. With a snorkel (which you don't have), you can go in DEEP water. All the snorkel does is take your cold air intake and move it up above the waterline. The only issues that most see in deep water is water getting in the alternator, diff's, etc. If they protect these things as well, they're good.
Without a snorkel, if you didn't drown it out, you're probably OK. Might want to check the oil in the diff's and spray the alty with silicone, but other than that, you should be good, as long as it wasn't floatin'!
-G