When can I go scuba diving after a thread lift?

Dear B.lessed,
Thanks for this thoughtful question. I will presume you are particularly concerned of a Face ThreadLift.
ThreadLift provides a “minimally invasive” approach to elevate the soft tissues of the skin and underlying (subcutaneous) fatty tissues. Performed correctly, the nearly “hair-thin” collagen stimulating, dissolving thread will produce a microscopic collagen or scar collar around the thread holding the tissues in place for 8 to 12 months. Initial elevation of tissues occur mechanically by massaging the fibers of the soft tissues up the series of barbs created in the suture. It takes the body 10-14 days before any collagen is first made by the immune response to the thread and only surrounding the thread(s) themselves, not the entire region. I estimate no less than 3 weeks from the procedure before a patient may begin significant movement, compression or lymphatic massage opposing the direction to the lift as it will dislodge the tissues from the barbs and lose the desired lift.
Swelling, water pressure on your mask occurring over the lifted threadlifted facial skin will therefore dislodge the effectiveness of the lift you are looking for within 3 weeks. I recommend waiting 6 weeks for adequate tissue stability from the procedure.
Please review the Surgeons recommendations with him/her as they may differ from mine. I hope this helps. All the best.