Help with bathymetry

[CoreyMcCormick]

Okay, here is my project, plans, and problems...
Project:
  I am a student currently interning at Roatan, Honduras at a dive resort.  One of the projects that I am trying to accomplish is to "map the sea floor" for the guest here.  The equipment I have to basically a dive computer that gives good enough depth reading so that it can be done. Then turn that into a 3D map.  I am using Arcmap 9.3.1 Student Edition.

Plan: Collecting Data
  Using my dive computer I am going to swim in lines to make a grid about 30 meters square.  This is a starting point to see if I will be able to do it.  My computer takes depth every second, I figure I can try and swim slowly to take as many measure along the path as I can get.
Plan: Using Arcmap
   My plan is to make a create a line and point shapefile, or maybe a grid.  Put points on the grid giving the data for depth.  Then putting it into 3D.

Problem:
   This project is pushing my limits of my understanding on how to do it and way do it.  I have always dealt with roads, or pre-made base maps.  So making a new map is very new to me.  If any of you know a good way to go about going about the project, could you give a basic outline on what to do?
Thanks,
  Corey

[SimonKettle]

Have you had a look at this? : http://www.uwec.edu/hartnesg/SeanWeb/BATHMAP/Bmap.html

I have not done this type of project before but it strikes me that you want to create a 3D Point file and add the data you collect for each point (do you have a means of swimming in precise lines, since I assume currents etc may make the mapping in-accurate to some degree [it depends how accurate you need to be for this mapping project]) you can use this data to make a DEM (Digital Elevation Model).

I have not done this process before but I believe you need to make a TIN (Triangular Irregular Network), Now you may not have the add-ins to do this as I believe it requires 3D Analyst/Spatial Analyst so have a look at these sites for more info on TIN Surfaces [http://www.ian-ko.com/resources/triangulated_irregular_network.htm] [http://webhelp.esri.com/arcgiSDEsktop/9.3/index.cfm?TopicName=An_overview_of_the_TIN_Surface_toolset... and find out if you can even do the processing required by checking what extentions you have, are you running the spatial analyst or 3D Analyst?.

If you make a TIN surface you can begin to make contours and a grid which you can manipulate to create images like below from http://www.uwec.edu/hartnesg/SeanWeb/BATHMAP/Bmap.html:

I hope this helps.