Play it slow. Keep their stuff off the board until you have enough juice to power a huge Anui or Kraken or Great Old One and finish it off with a ice lance for the last point.

You rarely move your Avatar.

Mostly use abilities and spells to move their minions into sites where they can/will drown.

Thin ice beside a Watery Grave is sweet, if you submerge a guille Sirens (holding an angel egg) under thin ice and pull their minions into it, the ice will break at 5 power when you surface...drowning their minion and then triggering a skeleton for you.

Overflow is key in building your body of water for Anui.

Devil's egg: give it to a Tide Niad or something else that can submerge; flood opponent's site, and submerge under there with the egg.

Wave Shaper can go tempo or slow control. This build is slow control.

Font of Life buys you more time. Often it can undo all the work your opponent has done; assymetrically resetting your game .

(If you know Landstill in MtG, that's my style). You can drop a shark and just sit behind it for a bit. More similar is the old Mono U Control filled with counters and removal and card draw + waiting for something like a Morphing to win the game once your opponent has been denied resources.