Aqua Prison has a long cooldown, make sure to use it at the right moment.
Using Ebb and Flow during an engagement with enemy champions will help sway the battle in your favor.
Nami's ultimate can come in very handy for initiating on enemies who are far away.
Aqua Prison is a very powerful ability with a long cooldown, take advantage of the situation if Nami misses this ability.
Tidal Wave has a very long range but travels slowly, be aware of when it is coming your way as you can move out of its path.
Try to avoid fighting an opponent affected by Tidecaller's Blessing, it lasts a short duration so waiting it out can help you greatly.