A cable laying ship is generally specific to laying and repair of submarine cable systems.
The first submarine cable ever laid was in 1850, which was a 20 mile cable between England and France.
The very first cable ship was a small paddle steamer named Goliath, which was used to lay the cross-Channel cable in 1850. Going forward standard merchant ships were used, the largest of which was the Great Eastern, which was used to lay the Atlantic cables of 1865 and beyond.
Custom-built submarine cable ships were first introduced with the Faraday in 1874, and have been used since. They are generally recognizable by the cable sheaves at the bow and/or the stern through which the cable is laid on the seabed and the specialist deck machinery used for the actual laying of the cable. In addition, they obviously need to have large holds as technology improved, the design of cable ships was continually updated.
TE SubCom operates a fleet of 8 ships (6 of which are Reliance Class). Modern cable ships like the vessels in the TE SubCom fleet utilise the latest technologies in order to lay submarine cables. Some interesting facts about Reliance Class vessels:
If you would like more information about Reliance Class vessels, have a look at the TE SubCom information brochure that can be found here: http://subcom.com/pdfs/brochures/RelianceClass.pdf.