In case you live in London .. come see the Science Museum (South Kensington), they have an incredibly cool deep-sea fish exhibit going on, including bioluminescent ones.
and i usually stay the night. 2 or 3 times that i've been there, i see massive bioluminecents in the water. not sure exacly what causes it. but in the middle of the night ill go into the ocean and spash and its the brightest purple you've ever seen. like when you hit the water it 'activates' something and explodes with color.
anyway. i do have the internet right here. should probably look that up. its amazing.
I was in a bay in the east of Puerto Rico last year where they had bioluminecent bacteria in the water, where you could kayak through. I guess it's not the same as going deep sea but it's a lot more in reach I guess - you could do it for a grand over a weekend :)
Road Block(s): No packaged trips to do this, no network with marine biologists/researchers who own the subs