Klondike hotel has been quite popular recently as we've had other people asking about the quality of service e..t.c.
It is not THAT popular though to have proper websites mentioning it...
I haven't been there personally but it is located in a remote part which is 10 mins walk from the busy Flic en Flac public beach. Unfortunately, it does not have a lagoon on its seafront but only rocks and brown sand so you'll have to rent a small car and drive a further mile or so to have the white sand and clear lagoon.
I used to fish around that area!!!!
With regards to your question about the roadmap, you'll be able to get one from your hotel or buy one at a reasonable price in the shops nearby.
Like good old stefan mentioned, the nearest undersea walk is located in Grand Baie which is like around 45 mins away and further north. Again, your hotel will have the information packages as they might have ventures with local people in Grand Baie who offer this wonderful thing (undersea walk).
Hope this helps