I should wait another tour group. So maybe 3 hours wasted. In addition, though I selected sea food lunch, I can eat only squid and octopus, not shrimp or lobster. Basically, though you can book online even before day which you want, you should call them. It depends on te tour, it may be available.
Except for some worn out life jackets, it was great. Excellent transport to and from the site...and crazy fun crew ans stff....do it.