A couple suggestions for the future:
Assuming the planning to penetrate the wreck was done on the surface, you and your buddy should discuss hand signals as well as alternate plans. Before entering an overhead environment you signal to your buddy "penetration" (roll up your hand, as if around a pipe, to make a "hole," and with the index finger on your other hand, "penetrate" that hole). Get an ok before proceeding. Either way, you should always have a plan in advance - if there's no plan/communication then there's no penetration.
The other suggestion is that both buddies should always be aware of where the other one is (even if you just paired with them for the first time). That's true for you as well as the buddy. Neither of you have a redundant air supply, so you're each others lifeline. What that means is that you should have been aware that your buddy didn't enter, because you're entering (or not entering) together.
I can't add much else that hasn't already been said by others. Based on the video it looked like a pretty benign penetration, but we must always remember that everyone has different levels of risk tolerance, training and skill. The last thing you want to happen is an "oh ****" moment inside any enclosed environment. That's not the place to panic and it's not hard to get a panic attack if someone isn't used to the environment and gets caught up in something. Logic goes out the window instantly and that's when problems happen.
Sounds like a fun dive, otherwise!