A couple weeks ago we got a new little guy that was in a candy snail shell and he immediately dug down into the sand and we haven't seen him since. I'm thinking this naked guy could be him and he may have ditched his shell before surfacing. There are 2 others about the same size/color in the tank though so it's possible it could be one of those instead.
We've had crabs for a little over a year now and I've gotten pretty confident in caring for them and not worrying about every small thing like I was at the beginning.

1. What kind of substrate is used in your tank and how deep is it? Play sand, 8-10 inches
2. Do you have gauges in the tank to measure temperature and humidity? If so, where are they located and what temperature and humidity do they usually read? 84% humidity, 81 degrees
3. Is a heat source used in the tank? If so, what? Large UTH attached to back of tank
4. What types of water are available (fresh or salt) and how is the water treated (what brands of dechlorinator or salt mix and what ratio is used to mix it)? Both-- Instant Ocean and Prime
5. What kinds of food do you feed and how often is it replaced? Variety of fresh fruits & veggies, dried mealworms/crickets/insects, dry mix with nuts, oats, dandelions, etc. replaced as needed (fresh replaced every day or two)
6. How long have you had the crab and what species is it, if known? Purple pincher-- had it anywhere from 3 weeks to 9 months
7. Has your crab molted, and how long ago did it happen? Unsure
8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing? 75 gallon tank, glass lid with hinged openings
9. How many crabs are in the tank and about how large are they? 9, varying sizes
10. How many extra shells are usually kept in the tank, if any? 25-30+ (not positive, didn't count them-- there are lots though)
11. Have there been any fumes or chemicals near the crabitat recently? No
12. How often do you clean the tank and how? Vinegar on glass as needed
13. Are sponges used in the water dish? If so, how are they cleaned? No
14. Has anything new been added to your crabitat recently? Yellow bell pepper 2 nights ago
15. Is there any other information you would like to share that might be helpful (anything that is regularly part of your crab care, playtime, bathing, etc.)? We pretty much just leave them be
16. Please describe the emergency situation in detail.