Hey AL!
In the Aquarium you can turn left or right and you will see a kind of red rail...you can go through it, down on few steps and you can jump in the water
Use the Z key to get a bit down then swim straight with the up arrow or with the help of the mouse. To swim up use the space bar.
Walking hand in hand is not available but as a VIP member you can send private message (right click on the other avatar and choose the option) so you can stay connected with your company. Also you can add other members to your friend list and find them in RLC: Friends button on the top, right click on the friend's name then choose Go there.
Probably you can find the message in My messages' inbox on your profile. You simply can reply your Guide's message so he/she will know you would like a tour.
I hope I could help
Regards,
_Shila_