If you select the cog/settings icon, you will be able to adjust the special effects slider to help your game perform better. A setting of 10 will mean lots of extra special effects like sunlight rays, fish silhouettes etc. but this can be a bit of a struggle for some devices. Adjusting the slider down should help.
Another thing that helps a device to run Splash properly is ensuring you have plenty of space (more than 2GB) and battery.