Scuba diving is a popular virtual sport in Second Life… and scuba diving has been available on the Virtual University of Edinburgh facilities in Second Life from the very earliest days of the Vue regions (back from 2006). See this blog post for some early images.
An up-to-date free set of Scuba Gear created by “SamBivalent Spork” in Second Life is available at the Diver Alert Network (DAN)…
http://maps.secondlife.com/secondlife/DAN/69/130/52
Scuba Dive Tour HUD
Pick up a copy of the (free) “DAN Branded Gear” also and try out the dive tour HUD… take care in the caves, and remember to follow the safety trail…
Scuba Dive in VR
Using the CtrlAltStudio viewer and the Oculus Rift, try a dive in virtual reality…