Bet you needed a fast shutter speed to catch this speedy little critter, lol.

I would just enter a new one in this place. go to "My stuff" then "my contest entries" and find this photo and should see something that says "edit entry". Then you can browse for a new photo, make sure to check the box "high resolution" and then click "submit" Having two photos very similar loses anonymity here which is not allowed. I wouldn't see there being a problem with the other one having 2 of each, but I'm not a mod so I can't be for sure. In my opinion, the other one is better.

Author you can red flag the entry you wish to remove, asking
the mods to remove it. But you should give a good reason as to why you request this. That still does not mean they will remove. But it is worth a try if you have a valid reason.
Another option is to edit. I do not see a problem though.
Good luck

I would get rid of this one and leave the other

Jelly fish do not represent relaxation to me. They represent stinging pain! IMO

That is why I always suggest ticking, full resolution.

I think this one could do with a levels adjustment to help it 'pop'