Mr Beast Tweeted on Jun 25, 2023 that "[he] was invited earlier this month to ride the titanic submarine, I said no. Kind of scary that I could have been on it." However, the screenshot, presumably from iMessage is blue. A blue message means that the person who screenshotted the message is the same as the sender. If MrBeast is posting his screenshot, the invitation message would presumably be either gray or green (as he shouldn't have been the sender).
He clarified that the screenshot of the invitation was sent to him by the person who offered it.
While the Twitter replies call this dubious, it seems even more dubious that he would post a fake text not remembering how colors work.
It's also not clear if he was being invited to join the doomed dive, or a later dive scheduled for "the end of this month" (June). Context implies the latter, as the roster for each dive seems to have been decided about a month in advance.
Two other YouTubers, Jake Koehler and Alan X El Mundo, were also invited at various points: Jake rode on the sub in early June and Alan had gone the previous year. So invitations may have been widely distributed to travel YouTubers.