Coconut octopus like this one generally use broken coconut shells as "homes." They live in the biggest part, and pull smaller pieces over the opening as a way of hiding. This female is really too big for the beer bottle she's using (holding the piece at right to try to close herself in), but since she has eggs - clearly visible at left), she still needs something in which to hide...so she's doing the best she can.
Blue-ring octopus (size of a plum) - very poisonous! This little "BRO" could have been in the "don't touch" section, as his bite will kill a human within 15 minutes, but I felt he should be here with his "kin." This was the first BRO many people on the trip had ever seen, even after 500-1000 dives. I've been lucky enough to see 3 others over the years, but seeing another one was still VERY cool!