When scuba diving, who enters the water first? The novice or the experienced diver?

That depends on how eager, considerate, responsible, respectful, etc., the novice and the expert divers are. There are no rules. Personally, I believe that the more experienced divers should go first, for a very simple reason: Should the novice have problems as soon as he/she jumps on the water, the more experienced ones are ready to provide help if necessary. I believe that it would be worse if a novice jumps out first, have problems, and have to wait until an experienced diver can jump out, make sure that his gear is ok, and then help the novice. We are talking about only a few seconds of difference, but this could mean a lot. (And yes, I'm a scuba diver).

There hasn't been any kind of order that I could tell in any of the diving I've done. Generally, everyone is so keen to get in the water that we're all splashing at or close to the same time.

Who's in the water first is mostly a matter of who's closest to the dive platform...

Usually you go in at the same time. It all depends on the situation. Sometimes the experienced will lead the way sometimes he has to heard up everyone and push them forward. Sometimes he has to wait till last because that is the best place to react if something happens. There is no set answer to this question.

Good luck