Penetrating a wreck is one of the few underwater activities that require an additional certification: the overhead environment adds an extra level of risk. Apart from proper training, bringing the right gears is also necessary in successfully diving a wreck site.
The basics of using a reel may be familiar to you if you are recently trained. You need a more robusts reel in wreck diving than the one you use for your Delayed Surface Marker Buoy (DSMB). DSMBs that use finger reels do deploy. However, while you are within a wreckt, these can be prone to tangling. A ratchet-style reel is a better option as it is less likely to tangle while it is being unwound. Also, these kind of reels are much easier to retrieve and less likely to jam.
Diving a wreck has the same concerns as doing a night dive. Wreck diving is limited to the light zone—light is necessary for safe navigation. The rule: bring one primary light and a secondary light. If the primary dies, use the secondary torch and immediately abort mission. A torch with a wide beam is generally recommended. The dive torches must also be easy to grip.
You should definitely wear a rashguard or a wetsuit when penetrating a wreck—even when you are diving in warmer waters. Sharp edges may be present inside the wreck, so a proper garb is needed to protect you from cuts or scrapes. Dive gloves are also a necessity—while the “do not touch” rule should apply, this is not always possible since some wrecks are tedious to explore.
A cutting tool will easily free you up in case of an entanglement—lines and cables within the wreck can easily snag you. Remember: the perfect dive knife is easy to handle and quick to release.