Underwater camera accessories

I am considering purchasing some accessories for my fantasea underwater housing and have a few questions:

1. Focus light - are these necessary for daytime diving?

2. Macro lens - I would prefer to buy a fantasea lens to go with my fantasea housing but this is twice the price of other macro lenses, if i go for the cheaper option will make any difference to the quality of pictures?

3. Red filter - would this be a good investment?

4. Strobe light - I am looking at the fantasea strobe kit, can anyone recommend a cheaper brand which still offers similar quality?

middlemef, I can't answer all of your questions with a great deal of specificity, but I can give my views on them, and maybe that will help direct your thinking and research.

1) Focus light--this is useful not only for making it possible for your camera to focus on the subject in the dark, but also for helping you see exactly where your strobe is pointing, even in the daytime.

2) Macro lens--the optics should be pretty much the same regardless of what brand you buy, as long as the brand is reputable (check with u/w photo discussion sites such as wetpixel for insight and reviews); the most important thing is to get a lens with the same sort of mounting system as your housing permits--not sure if fantasea has a threaded mount or a different sort.

3) Red filter--you only need this if you are not setting your white balance manually, which is a better method anyway; additionally, if you use a strobe, you don't even need to set the white balance--any additional tweaks you need to make can be done in the digital darkroom.

4) Strobe values--sorry, can't help here. I use an Inon D2000 strobe; my dive buddy uses an Ikelite DS50, which are both good models; one thing to consider is how the strobe will synchronize with your camera to fire.

Thanks Quero.

With respect to 4), how else does a strobe synchronise with the camera other than a sensor over the built-in flash? and which method is preferable?

Depending on the camera and housing, there are other means of synchronizing the shutter opening with the strobe flash. One of these is called TTL, for example. Whether this option is available to you depends on the type of camera, housing, and strobe you have. You should probably write to Fantasea's customer service for details concerning your specific options.

Just to make yourself confortable, I have been photographying underwater for 8 years and been from compact into a plastic housing to pro dSLR in alu housing, two strobes with all the bells and whistles.
I will tell you honestly what experiences taught me.

I would say (I suppose you have a compact camera)
1- buy yourself a good reliable strobe. That's something you're going to keep don't go cheapo, forget Fantasea which is crap. pay yourself either a Inon or a Sea&Sea.
2- A macro lens is nice, Inon does nice wet macro lenses with M67 thread.
3- A focus light : the Inon 250 is a very nice and powerful one
4- A better housing (I've had a Fantasea... you'll soon need to change.. believe me... :) ..)

@Quero, "One of these is called TTL, for example." To be very precise TTL is not a sync type, it's a light measurement process. There are two usual sync types : optical (cable) and electrical (with a sync cord).
The newer housings even for dSLR tend to favor optical sync because you can have eTTL or iTTL with any brand of cameras whereas true TTL is only available most of the time with Nikons and lectrical sync, or with Canon+very expensive strobes having 6 pins connection.