NOTE: My Review research after 15 minutes of online research & from personal experience:  

1. Shore Excursion Group: mostly positive; On Time Ship Rerturn guarantee PLUS $1,000 USD
       per customer for inconvenience of missing ship.

2. Your Guide: mostly positive … 

3. Tours by Locals: mostly positive except for full group prepay requirement;
           “… think Viator, but a lot better run…”, with both clients & guide support, &
          dispute resolution service that works. Guides curated before being listed. 

CRITICAL Guarantee: If late to boat … guarantee to, “ arrange for and cover the costs of overnight accommodation and transportation to your next feasible port-of-call.”

4. Trip Advisor & Viviator (TripAdvisor company): AVOID, unreliable & overpriced.
            TIP: read a page or 2 of reviews on these organizations, BUT NOT reviews on their site