wcif a lot or a world with corals everywhere like this picture ( http://nilxisdesigns.blogspot.fr/20...glish-info.html ) [URL=http://2.bp.blogspot.com/-LvAah2wroUc/Uh0S1WuqP2I/AAAAAAAAAls/rc6X25DC_TA/s640/o.jpg [/URL]
and why my sim don't want go under the sea ?

I play Suvadiva as a vacation spot for my sims. Love that little world. I do not know where to find another world with corals everywhere but what you can do is copy the dive spot to your library and place it in any world deep enough to accommodate the dive spot. See Docks, Ports And Dive Spots at the bottom of the page. You can also add corals to existing dive spots using the buydebug on cheat to access water objects.

For sims that do not want to go under the sea perhaps they do not have a high enough skill level for diving. Not sure what the level it is but should you want to increase the skill level without doing all the work there is a setting in Master Controller to apply more skill points. From City Hall or a computer>NRaas>Master Controller>Sim>Advanced>Skill Level. The MC Cheats module is needed.