The cache is available only during the cold season (from November to March), when Herastrau Lake is fill out of water.
Of course you can dive during the summer time, but the cache is linked to the bottom of the lake, so you will distroy the logbook by opening the cache.
Only loogbook and pen. Please maintain the box if necessary and put in in good conditions, considering it will be 3/4 of the year under water.
Enjoy!
CarpatBike