I've never looked at this particular combination so just some subjective comments after a quick review.
Ikelite is certainly a quality housing. But I don't think the "SuperEye viewfinder magnification" will be of much use since the camcorder doesn't have one....
I quickly looked at the
camcorderinfo.com review and the thing that jumped out at me immediately was the abysmal low light performance they measured - 15lux. Sony's latest HDV camcorders by comparison claim 2lux. This would be a big problem in low light situations and would require lights for good results.
Another thing I noted from the comments at the bottom of the page is that the camcorder goes into powersaving 5mins. after being on standby. That could be pretty unwieldy in a housing and might cause you to miss the unexpected "great shot" while the camera powers back up.
Some general comments: Most u/w videographers use Sony gear. So more manufacturers provide housing options for the various models. Sony just introduced several new HDD models, all have larger capacity than the JVC. On a long trip (liveaboard?) it might be possible to fill 30GB's of HDD then you'd have to dump it all to a laptop or some other storage device.
I also recommend to anyone that they consider HDV if it's even remotely possible within their budget. Guesstimating yours it could be for an extra $5-700 or so. Everything is going HD, the output of this camera on an HDTV set will likely be disappointing.
Also, Ikelite housings are pretty model-specific. And that's not a new camcorder so it's doubtful that their current models will match the control locations in the future. Buying one of the affordable electronic models - TopDawg, Ocean Images etc. may provide a better upgrade path.
my .02
