All About Mojo

I have a challenger 180 (2007) with brand new battery for dealer. I bought boat to cruise around but plan on chilling on water with radio on often, but worried about draining battery. Thoughts on adding 2nd battery?

Hook up 2nd in parallel and charge/use both at same time (very easy install). In this case hook up trickle charger to one or both batteries?

Hook up 2nd with additionsl 1-2-1/2-off switch? In this case I know trickle charge them separate.

Ps...I have a double trickle charger already and like option 1 because easy.

Thanks