The solution was to specify display levels on both of the layers I wanted to use (as the previous user suggested). I also made sure to not use the same level (10) in both layers.
basemap = new esri.layers.ArcGISTiledMapServiceLayer("http://server.arcgisonline.com/ArcGIS/rest/services/Canvas/World_Light_Gray_Base/MapServer",{displayLevels:[10,11,12,13,14,15,16]});
map.addLayer(basemap); //added this layer so there would be a large number of zoom levels and for overview map
oceanBM = new esri.layers.ArcGISTiledMapServiceLayer("http://server.arcgisonline.com/ArcGIS/rest/services/Ocean_Basemap/MapServer",{displayLevels:[0,1,2,3,4,5,6,7,8,9]});
map.addLayer(oceanBM);