As long as you stick with the ship's excursions you will be back on board in time for sailing no matter what. They have held ships in port several times because a tour was late. I recall one time we had to pull away from the dock so another ship could come in, but a group had not returned. They ended up tendering the group from shore before sailing. I cant say that they would wait for you if on a non-ship's excursion. That being said, there are some great alternatives out there that are very good about getting you back in time. Check around these boards for posts about those companies (most are for other locations that youre not going to this trip). To be safe when using non-ship's I would book an early morning trip that doesn't last all day. Weather, transportation problems, lagging guests from other ships can delay your return easily! Have a great time!