Would this fit a Nikon D40 with Nikon's new 18-300 lens? Fully extended, body + lens = 11.5 inches. Lens itself goes from roughly 5.5 inches to 9 inches. Body is 5 x 4 x 3.
I have the Canon Rebel XT with a lens that goes to 300. I don't know if it will fit with it fully extended but it comes pretty close. I have found I don't have to extend the lens as much underwater since water helps magnify already. I have really enjoyed being able to take my camera underwater and have gotten some great pics of sea turtles, etc. Hope this was helpful!
I have the D7000 with 70-300 lens. Fully extended body + lens = 10.5 inches (lens is 8 inches fully extended). This just barely fits on the Aqua-458 so based on that I expect your 18-300 would fit but may not fully extend.