The antithesis of BASE
I know this is kind of the opposite of BASE jumping, but I guess you could still pull low if you wanted to. :-) http://blog.scifi.com/tech/archives/2007/06/26/diving_from_spa.html
http://www.popsci.com/popsci/aviationspace/3c082d2daa463110vgnvcm1000004eecbccdrcrd.html