Jessica Love-Amaru, of Titahi Bay, is baptised by Brother Davidson on Saturday as part of a nationwide plunge for members of the New Zealand's Jehovah's Witnesses.

More than 17,000 Jehovah's Witnesses gathered around the country for their national convention on Saturday, including more than 2000 at Porirua's Te Rauparaha Arena.

Convention news service overseer Rick Delmarter said the congregations were satellite linked with two conventions each in Auckland and Hamilton and another one in Christchurch joining the faithful in Porirua.

The convention theme "Safeguard Your Heart" is based on Proverbs 4:23, with strengthening personal spirituality the focus of the programme.

The three-day event runs until tomorrow with daily themes based on passages of Scripture, including 1 Samuel 16:7, 1 Chronicles 28:9, and Matthew 12:34.

"The talks were really well received - we spoke about our desires and ambitions and how we can have a balanced view of ourselves and focus on Bible principles," Mr Delmarter said.

Non-witnesses are welcome, in fact encouraged, to attend the open and free convention.

"We are well aware that Jehovah's Witnesses are not the most popular religion on the planet, but our intentions are noble and we genuinely desire to help people learn," Mr Delmarter said.