5. Vessels, Net

	Cost		Accumulated depreciation		Net book value
Balance, April 1, 2015	439,180,669		(19,204,616	)	419,976,053
Additions	241,450,881		—		241,450,881
Disposals	(268,281	)	26,060		(242,221	)
Depreciation	—		(4,749,861	)	(4,749,861	)
Balance, June 30, 2015	680,363,269		(23,928,417	)	656,434,852

The additions for the three months ended June 30, 2015 represent amounts transferred from Vessels under Construction relating to the cost of our newbuildings, the Cougar, the Concorde and the Cobra, which were all delivered to us in June 2015.

Vessels, with a total carrying value of $652.6 million and $416.0 million as of June 30, 2015 and March 31, 2015, respectively, are first-priority mortgaged as collateral for our long-term debt facilities (refer to Note 7 below). No impairment loss was recorded for the periods presented.