That's cool I thought the Marathon looked awesome. If you've never owned a Seiko before this might help. I've never owned a "Monster" but from previous experience with quite a few Seikos, Including auto divers (which are VERY TOUGH), I'm sure it's tough as nails. You might also want to check out a Citizen Ecodrive PRO Model, I really like eco-drives and have had very good experience with them. In fact my Eco-drive Skyhawk (which I'd recommend if you like Pilot watches) only gains about 4secs/year, the most accurate watch I've ever seen in person. The only thing with the Pro Diver Citizen is that the case is so THICK (I think it's 18mm or more) that to me it is very uncomfortable to wear in Stainless but they also make it in Titanium and to me the Ti model is so much lighter that the thickness doesn't bother me in fact I think it is very comfortable. An also if you are really into visibility in the dark I've found Seiko's Lumnibrite to be FAR SUPERIOR to whatever Citizen paints their hands and dials with but the Diver model Citizens do OK in that respect due to the size of the hands and markers.
I have quite a few Citizens, Seikos, and Timexes for now no Swiss ownership but I hope to change that in the not too distant future, I like Rolex and Omega and aside from the Submariner I think the Marathon SAR with bracelet is the best looking divewatch I've seen at least in photos. I like the looks of Luminox but I always hear mixed reviews, regardless of model one person says they are indestructible and the next says it'll fall apart etc. so I've kinda held off on buying one even though I really like the looks. IF only Seiko made their 007 with tritum vials and a Hamilton style dial, now that would be PERFECT.
UMM I just discovered something else, Traser watches, they make a yellow diver with black case but it is PVD coated Stainless Steel instead of plastic, I really like the less cluttered dial than the luminox and the steel case, otherwise it looks like a yellow faced "navy seal" watch which is what I was considering, anybody got any info/opinions on Traser watches?