In Lembeh, you can see these guys on most dives. Often you will swear that there are none around, but if you sit very quietly on a slope at 30 - 50 feet, suddenly you will notice a clump of muck moving. Approach, and it will bloom before your eyes "walking" along the bottom. Push it and it will jet 5 meters, hit the bottom, turn muck-colored and "disappear".
Eggs are relatively easy to find and there seems to be some synchrony in hatching since every now and then hundreds of 1 inch hatchlings show up in the area.
Photographing these guys is worth the trip alone.
Roy