"Why be baptised?  The answer to this question is not too difficult to discover. We simply have to remember that a Christian is someone whose experience of life has been blessed through their surrender to Jesus Christ as their Lord and Saviour. Out of love and loyalty to Jesus, the Christian will gladly take to heart what Jesus expected of those who declared themselves his loyal followers. Baptism is no exception to this rule. To be baptised is to obey.
"Why do it like that!?"  In the days of Jesus and the early church, 'baptise' was a soaking word. It meant to be 'immersed', or 'drenched'. Many churches today believe it right to take this quite literally. Some are baptised in this way in the sea, others in rivers, and sometimes a public swimming pool is hired for the occasion. Here at Worle Baptist Church, a large tank is one of our fixtures and fittings!

To get thoroughly wet or drenched is entirely appropriate when you understand how baptism was understood in the New Testament:
... being washed  "Be baptised and wash your sins away,calling on his name" (Acts 22:16)
Water washes, and helps make clean. The Bible makes it clear that we are mysteriously and wonderfully cleansed through the blood of Jesus shed on the Cross. Baptism by immersion helps us picture total forgiveness and complete cleansing. No bit us is left out! 
... death/burial/resurrection  Paul, one of the greatest of the first generation of Christian leaders, understood baptism in terms of dying with Christ,  being buried with Christ, and rising to new life in Christ. When a Christian is baptised, the old life without Christ is declared dead and buried, and his/her new life as a devoted follower of Christ is proclaimed.
... the Holy Spirit  That new life cannot, however, be experienced without another very special gift of love from God. Not only did he give his Son to live, die and conquer death for us, he also gives us the precious gift of his Holy Spirit. In coming to faith in Christ, the Bible speaks of us being baptised in the Spirit and of being continually filled with the Spirit. No half-measures here either! Baptism speaks loudly of the Christian's receiving the Holy Spirit fully into his/her life so that sin may be conquered and life in all its fullness explored and enjoyed. Through the Spirit, Christians also receive heavenly strength and comfort to help us cope with those difficulties of life that come our way in some measure or another.

Baptism, then, is a powerful witness to the rich grace of God to those he dearly loves. And it is the witness of the believer to his/her love and dedication to God.

"Is it only symbolic?"  Baptism symbolises dramatically everything already mentioned. But the symbol is connected to its reality. Baptism is an 'interface' between the material and spiritual realities in which we live. The same is also true of the Bible. It can be no more than print on a page just like any other book. But the Christian who has met with God through Scripture knows that it is far, far more than just another book. The very words that speak to our minds of spiritual realities, bring those realities home to our hearts.
Baptism is thus more than just getting thoroughly wet! It is a meeting point with God. In baptism, the believer can expect the things it symbolises to be experienced in some way or another.

A lot more could be said, but we hope that this short explanation will enrich either your own baptism or your appreciation of a service of believer’s baptism that you might be present at.