Koi Samui snorkelling tours, pick up from cruise ship pier

[Maple30]

 

We'll be on the Diamond Princess and docking at 9am, departing 5pm on the 3rd March. I've enquired about snorkelling and a tour company said the tours will depart before we'll get off the tender. Anyone had any success picking up a snorkelling tour at the pier? I'll be going solo, can swim and snorkel but am in my late 60's so don't want any 'adventurous' tours. Any help very much appreciated. Or, alternatives for another land based tour including my husband.