Some fishing boats include a livewell system. This document describes livewell systems that have multiple modes of operation. The modes of operation include, at least, a first mode with a lower water level and a second mode with a higher water level. While the livewell is operating in the second mode, the tank is nearly full of water. Accordingly, with a nearly full tank, the water in the livewell will resist sloshing around while the boat is navigating rough seas or travelling at high speeds or for long distances. Moreover, the health of the fish in the livewell will be protected because of the water's lessened tendency to slosh around in the livewell.