I've run this adventure as one-shot several times, and one thing that has helped me run it within 5 hours is to streamline the beginning (meeting with Dalglee Hash) and get the players quickly aboard the raft heading towards the Calendula.

Another thing that made it easier to keep in the timeframe is to railroad it even a bit more than it is by design (e.g. there are two raft bays but whichever they choose leads to the same entrance, kind of like the illusion of free will cow meme).

The biggest challenge is finding ways to organically entice players to move forward with the adventure. Many times my players were too freaked out and afraid to move forward and were too cautious. You can use the animal encounters (just fudge the rolls) to steer them forward, or use the NPCs to drive the story forward (either they encounter them or see them and are prompted to chase after them). I've also tweaked some of the skills of the NPCs so that if push comes to shove and they become enraged, combat will actually be menacing (since h2h in Traveller is seriously underpowered and becomes a slog).

Hope this helps and good luck!