Cave descriptions are written at the end of the survex block - between *begin and *end statements. Conventionally just after the QMs and before the *end .
The description is written as a single long line of text. In the online editor it is wrapped to fit the window.
;------------
[from couldashouldawoulda_to_bathdodgersbypass.svx]
;Cave description ;(leave commented-out)
; See 2017 description for details of GSH up to the 'p50'.
Briefly, on the way to couldashouldawoulda a 22 m entrance crawl from the
surface leads to a climb down and a junction. Left leads to easy c
rawling passage for a short distance, then another junction where
traversing over a shallow hole and down a stooping-height sandy
passage to a sharp left turn and a sandy, easy 'squeeze' leading to a
straighforward p10.
You can have several lines of description, as you can see if you follow the link above, but each one must be prefixed with a semi-colon otherwise the survex software will complain.
Technical Note: The syntax for a Cave Description, both the title and the text includes a leading semi-colon. So it is syntactically a "comment" so far as the survex software is concerned.