Depends on what you are looking for. Osprey dives in mid-October could be a hit or miss thing, most likely miss as they do not normally schedule after the end of Sept. Weather comes up fast. As for temps anything under 70-80 ft or so you most likely will be looking at 38-42 degrees.
The op is a great outfit to dive with. Did all my heliotrox classes with them. You will also find that they don't normally do shallow stuff. There are a couple wrecks they do in the 90 foot range but most are in the 100+ range. My last was in 165 ft. You also must be aware that unless specific sites are listed in advance the majority rules as to where they go. Also first person/group to book has a big say in this. They do ALOT of tech trips. I've been out with them 5 times and except for one trip everyone was in drysuits with doubles, stages, O2 for deco etc. Erie is not alot of fun diving wet off of a boat. It's cold. The good stuff is deep(100Plus) so unless you are willing to deco you won't get much time and if you want time you need to dive dry. The one trip where people were diving wet was only two of them, they were diving with 14mil over the core, and they were too cold to do the second dive. First was to 120, second to 95-100ft. Also it's very easy to go out on Erie in mid-October and run into a snow storm when 100 miles south the temps could be in the 60's-70's.
I just checked their site and no dives are scheduled for later than sept 29. They even state that this may be the last run this season. It is the St. James- 165 to the bottom- deck is at 153-155-(it's a beautiful wreck BTW) and three weeks ago the bottom temp was 39. Anything but a dry suit would be asking for trouble. There are some shallower dives next week(90-100ft) and the week after but you are still looking at 40-45 degree bottom temps. Overall diving in Erie is great! Vis normally in the 40-80 ft range and I've had as good as 100 plus. And even at 150 ft a light was needed for details. It would have been possible to navigate the wreck without one. Would not see much but you could have found the upline.
So short answer IMO- drysuit is necessary, diving in Erie is great with the right experience and training, it's friggin cold where the good stuff is, Osprey is a first class operation, to do it properly plan on using doubles or really big singles. And unless you are real lucky they probably will not even go out that late in the season unless you book the whole boat and even then if it gets crappy that day on the lake they will not risk the lives of themselves, the divers on the boat, and the boat itself.
