Caving

[ralreegorganon]

https://en.wikipedia.org/wiki/Caving_equipment

https://en.wikipedia.org/wiki/Single-rope_technique

Rivers
Lakes
Bio-luminescence
https://worldbuilding.stackexchange.com/questions/44335/how-would-a-cave-civilisation-survive-underground
sinkholes
cavefish

https://caving.susu.org/resources/SUCC-Kit-Buying-Guids.pdf
http://www.cavediggers.com/vertical/8ORG.pdf
http://www.crazycaver.com/content/beginning-srt-gear-list
https://www.ebay.com/str/inglesport/Caving-Equipment/_i.html?_storecat=49258582013
https://www.karstsports.com/kits-and-packages/
https://www.innermountainoutfitters.com/categories/caving/?sort=featured&page=3
http://www.warmbac.com/listing_accessories.php#socks
https://exploringcaves.wordpress.com/2017/01/19/best-caving-gear-for-beginners/
http://www.indiana.edu/~iusc/equipment.html
http://caves.org/grotto/ccg/docs/checklists/Checklist%20of%20Caving%20Equipment.pdf
https://www.kcgrotto.org/docs/caving_equipment_checklist.html
https://www.thoughtco.com/your-essential-caving-equipment-755632

handheld cave mapping seismic based / ground penetrating radar (use to reveal caves out to some radius) - at overmap and local map level