Depends which wrecks (of course). Most people "penetrating" a wreck would be superficial, for example dropping down into a hold and so on. Others are possible to get through the wreck in the corridors, but that's not as normal (wrecks decay and collapse in). Newer wrecks are more interesting with routes through (e.g. Hispania and Breda near the Sound of Mull).
The twinset/sidemount rig's important as you've got plenty of reserves should you get a little caught out; someone's flapped a fin or gone into the silt and screwed your visibility, so you need to slowly back out and wait for it to clear. Gas anxiety is really bad for stress levels (one of the big benefits of a rebreather).
The twinset/sidemount rig's important as you've got plenty of reserves should you get a little caught out; someone's flapped a fin or gone into the silt and screwed your visibility, so you need to slowly back out and wait for it to clear. Gas anxiety is really bad for stress levels (one of the big benefits of a rebreather).