All data layers in SeaSketch are map services hosted somewhere on the Internet. In some cases, those map services may not be accessible because the host computer is down, malfunctioning or overloaded. In these cases, SeaSketch displays a red icon with an exclamation point next to the name of the layer and clicking on the check box next to the layer name will not show the layer. 

If the problem is caused by anomalous Internet traffic, it may be resolved on its own. In this case, refresh your browser or check back later to see if you can turn turn the layer on. If the problem persists, users should contact the project administrator for assistance. 

If there is a legitimate problem with the map service itself the project administrator must take action to resolve the problem. Here are some things a project administrator should consider:

• Determine if you are using dynamic or cached map services. Many map service providers use dynamic map services because they are easy to maintain and do not require a great deal of storage space as do cached map services. However, if map services are updated and the feature list changes, this may break the link to the map service in SeaSketch. For this reason, we always recommend using cached map services. 
• Locate the URL associated with your map service by referencing the original source. For example, if you found the layer referenced in ArcGIS Online, locate that service again and copy the URL back into SeaSketch. If you continue