Close by but now apparently dried up, Pastscape records the site of “St Boniface Wishing Well” (SZ 5676878118):
“St. Boniface Wishing Well”, a spring formerly much venerated, especially by seamen, because an impervious stratum caused it to rise high up on the side of a chalk down.
From “Undercliff of the IOW”, 1911, 118-9. (J.L. Whitehead)
From Ward Lock’s Illustrated Guidebook:
The Wishing Well is interesting to the geologist on account of its unusual height, and to the superstitious from the reverence formerly paid to it on account of a popular belief that if one achieved the difficult feat of climbing to the spring without looking backward, any three wishes formed while drinking its waters would be gratified.
invectis.co.uk/iow/wl_ventnor.html