I am planning a diorama showing a group of radio control boat enthusiasts on the edge of a small lake, the focal point being a model of HMS Invincible being brought back to the bank. In the background will be other members preparing their boats for their turn on the water. I have the idea of using a picture frame as the base, build a raised section for the bank, and fill the lake area with tinted acrylic gel 'water. I tend to paint my diorama bases matt black, which seems to work perfectly against the natural colours of the groundwork. With the black frame surrounding the water area, would this suggest to the viewer that the lake actually stops there? Is there a better way of implying that this is just a small part of the lake?

A mirrored strip?

Not exactly sure how to pull it off, but you might try this; the side of the frame where it meets the lake water, remove that portion of the frame. Sort of similar to those "infinity pools" on the tops of hotels, etc.

Hmm ... good suggestions ... I really need to give this some thought.